JP2020065298A - Receiving device and communication system - Google Patents

Abstract

To provide a receiving device capable of enhancing communication performance.SOLUTION: A receiving device of the present disclosure includes a first receiving unit that receives one or more transmission signals and outputs a first output signal; an equalizer that equalizes the one or more transmission signals; and a second receiving unit that receives the one or more transmission signals equalized by the equalizer and outputs a second output signal. The equalizer selectively equalizes the one or more transmission signals on the basis of transition patterns of the one or more transmission signals.SELECTED DRAWING: Figure 33

Description

  The present disclosure relates to a receiving device that receives a signal, and a communication system including such a receiving device.

  2. Description of the Related Art With the increasing functionality and multifunction of electronic devices in recent years, various devices such as semiconductor chips, sensors, and display devices are mounted on the electronic devices. A large amount of data is exchanged between these devices, and the amount of data is increasing in accordance with the increasing functionality and multifunction of electronic devices. Therefore, data is often exchanged using a high-speed interface capable of transmitting and receiving data at, for example, several Gbps.

  Emphasis (pre-emphasis, de-emphasis) and equalizers are often used to improve communication performance in high-speed interfaces. Pre-emphasis is to emphasize high frequency components of a signal in advance during transmission (for example, Patent Document 1), and de-emphasis is to reduce low frequency components of a signal in advance during transmission. Further, the equalizer increases the high frequency component of the signal at the time of reception. As a result, in the communication system, the influence of signal attenuation due to the transmission path can be suppressed, and the communication performance can be improved.

JP, 2011-142382, A

  As described above, in communication systems, improvement in communication performance is desired, and further improvement in communication performance is expected.

  The present disclosure has been made in view of such problems, and an object thereof is to provide a receiving device and a communication system capable of improving communication performance.

  A receiving device according to an embodiment of the present disclosure includes a first receiving unit, an equalizer, and a second receiving unit. The first receiving unit receives one or more transmission signals and outputs a first output signal. The equalizer equalizes one or more transmission signals. The second receiving unit receives one or a plurality of transmission signals equalized by the equalizer and outputs a second output signal. The equalizer selectively equalizes one or more transmission signals based on the transition pattern of one or more transmission signals.

  A communication system according to an embodiment of the present disclosure includes a transmission device that transmits one or a plurality of transmission signals and a reception device that receives one or a plurality of transmission signals. The receiving device has a first receiving unit, an equalizer, a second receiving unit, and a selection control unit. The first receiving unit receives one or more transmission signals and outputs a first output signal. The equalizer equalizes one or more transmission signals. The second receiving unit receives one or a plurality of transmission signals equalized by the equalizer and outputs a second output signal. The selection control unit selects one of the first output signal and the second output signal based on a transition pattern of one or a plurality of transmission signals.

  In the receiving device and the communication system according to the embodiment of the present disclosure, the one or more transmitting devices are received by the first receiving unit, and the first output signal is output. Further, the one or more transmission devices are equalized by the equalizer, and the one or more transmission signals equalized by the equalizer are received by the second receiving unit, and the second output signal is output.

  According to the receiving device and the communication system according to the embodiment of the present disclosure, the first receiving unit receives one or more transmission signals, and the equalizer performs equalization on the one or more transmission signals. Since the second receiving unit receives one or a plurality of transmission signals equalized by the equalizer, the communication performance can be improved. Note that the effects described here are not necessarily limited, and any effects described in the present disclosure may be present.

FIG. 1 is a block diagram illustrating a configuration example of a communication system according to an embodiment of the present disclosure. It is explanatory drawing showing the voltage state of the signal which the communication system shown in FIG. 1 transmits / receives. It is a block diagram showing an example of 1 composition of a transmitter concerning a 1st embodiment. It is explanatory drawing showing the transition of the symbol transmitted / received by the communication system shown in FIG. 4 is a circuit diagram illustrating a configuration example of a transmission unit illustrated in FIG. It is a block diagram showing an example of 1 composition of a receiver concerning a 1st embodiment. It is explanatory drawing showing an example of the receiving operation of the receiver shown in FIG. 4 is a table illustrating an operation example of the signal generation unit illustrated in FIG. 3. FIG. 4 is a waveform diagram illustrating an operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 6 is a waveform diagram illustrating another operation example of the transmission device illustrated in FIG. 3. FIG. 11 is a waveform diagram illustrating an operation example of a transmission device according to a comparative example. FIG. 11 is a waveform diagram illustrating another operation example of the transmission device according to the comparative example. 9 is a table illustrating an operation example of a signal generation unit according to a modification of the first embodiment. FIG. 11 is a block diagram illustrating a configuration example of a transmission device according to another modification of the first embodiment. 21 is a table illustrating an operation example of the signal generation unit illustrated in FIG. 20. It is a block diagram showing an example of 1 composition of a signal generation part concerning other modifications of a 1st embodiment. 9 is a table illustrating an operation example of a signal generation unit according to another modification of the first embodiment. FIG. 9 is a waveform diagram illustrating an operation example of a transmission device according to another modification of the first embodiment. FIG. 11 is a waveform diagram illustrating another operation example of the transmission device according to another modification of the first embodiment. FIG. 11 is a waveform diagram illustrating another operation example of the transmission device according to another modification of the first embodiment. FIG. 11 is a waveform diagram illustrating another operation example of the transmission device according to another modification of the first embodiment. FIG. 11 is a waveform diagram illustrating another operation example of the transmission device according to another modification of the first embodiment. FIG. 11 is a waveform diagram illustrating another operation example of the transmission device according to another modification of the first embodiment. FIG. 11 is a waveform diagram illustrating another operation example of the transmission device according to another modification of the first embodiment. FIG. 11 is a waveform diagram illustrating another operation example of the transmission device according to another modification of the first embodiment. FIG. 11 is a waveform diagram illustrating another operation example of the transmission device according to another modification of the first embodiment. FIG. 11 is a waveform diagram illustrating another operation example of the transmission device according to another modification of the first embodiment. FIG. 14 is a block diagram illustrating a configuration example of a communication system according to another modification of the first embodiment. FIG. 27 is a block diagram illustrating a configuration example of a reception device illustrated in FIG. 26. FIG. 27 is a block diagram illustrating a configuration example of a transmission device illustrated in FIG. 26. FIG. 11 is a waveform diagram illustrating another operation example of the transmission device according to another modification of the first embodiment. FIG. 11 is a waveform diagram illustrating another operation example of the transmission device according to another modification of the first embodiment. It is a block diagram showing an example of 1 composition of a transmitter concerning a 2nd embodiment. FIG. 32 is a circuit diagram illustrating a configuration example of a transmitting unit illustrated in FIG. 31. It is a block diagram showing an example of 1 composition of a receiver concerning a 2nd embodiment. FIG. 34 is a waveform diagram illustrating an operation example of the receiving device illustrated in FIG. 33. FIG. 34 is a waveform diagram illustrating another operation example of the receiving device illustrated in FIG. 33. FIG. 34 is a waveform diagram illustrating another operation example of the receiving device illustrated in FIG. 33. FIG. 34 is a waveform diagram illustrating another operation example of the receiving device illustrated in FIG. 33. It is a perspective view showing appearance composition of a smart phone to which a communication system concerning an embodiment is applied. It is a block diagram showing an example of 1 composition of an application processor to which a communication system concerning an embodiment is applied. It is a block diagram showing an example of 1 composition of an image sensor to which a communication system concerning an embodiment is applied.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be given in the following order.
1. First embodiment (example using emphasis)
2. Second embodiment (example using an equalizer)
3. Application example

<1. First Embodiment>
[Configuration example]
FIG. 1 illustrates a configuration example of a communication system to which the transmission device according to the first embodiment is applied. The communication system 1 is intended to improve communication quality by pre-emphasis.

  The communication system 1 includes a transmitter 10 and a receiver 30. In the communication system 1, the transmitter 10 transmits signals SIGA, SIGB, and SIGC to the receiver 30 via the transmission lines 9A, 9B, and 9C, respectively. The signals SIGA, SIGB, SIGC respectively transit between three voltage states SH, SM, SL. Here, the voltage state SH is a state corresponding to the high level voltage VH. That is, the voltage indicated by the voltage state SH includes, in addition to the high level voltage VH, a voltage when pre-emphasis is performed on the high level voltage VH, as described later. Similarly, the voltage state SM is a state corresponding to the middle level voltage VM, and the voltage state SL is a state corresponding to the low level voltage VL.

  FIG. 2 shows the voltage states of the signals SIGA, SIGB, and SIGC. The transmitter 10 transmits the six symbols "+ x", "-x", "+ y", "-y", "+ z", "-z" using the three signals SIGA, SIGB, and SIGC. For example, when transmitting the symbol “+ x”, the transmission device 10 sets the signal SIGA to the voltage state SH (for example, the high level voltage VH), the signal SIGB to the voltage state SL (for example, the low level voltage VL), and the signal SIGC. To the voltage state SM (for example, the medium level voltage VM). When transmitting the symbol “−x”, the transmission device 10 sets the signal SIGA to the voltage state SL, the signal SIGB to the voltage state SH, and the signal SIGC to the voltage state SM. When transmitting the symbol “+ y”, the transmission device 10 sets the signal SIGA to the voltage state SM, the signal SIGB to the voltage state SH, and the signal SIGC to the voltage state SL. When transmitting the symbol “-y”, the transmission device 10 sets the signal SIGA to the voltage state SM, the signal SIGB to the voltage state SL, and the signal SIGC to the voltage state SH. When transmitting the symbol “+ z”, the transmitter 10 sets the signal SIGA to the voltage state SL, the signal SIGB to the voltage state SM, and the signal SIGC to the voltage state SH. When transmitting the symbol "-z", the transmission device 10 sets the signal SIGA to the voltage state SH, the signal SIGB to the voltage state SM, and the signal SIGC to the voltage state SL.

  FIG. 3 illustrates a configuration example of the transmission device 10. The transmitter 10 includes a signal generator 11, a register 12, flip-flops (F / F) 13 to 15, and a transmitter 20.

  The signal generation unit 11 obtains the symbol NS based on the symbol CS, the signals TxF, TxR, TxP, and the clock TxCK. Here, the symbols CS and NS respectively indicate any one of the six symbols "+ x", "-x", "+ y", "-y", "+ z", and "-z". Is. The symbol CS is the currently transmitted symbol (current symbol), and the symbol NS is the symbol to be transmitted next (next symbol).

  FIG. 4 shows the operation of the signal generator 11. This FIG. 4 shows six symbols "+ x", "-x", "+ y", "-y", "+ z", "-z", and transitions between them.

  The signal TxF causes a symbol transition between “+ x” and “−x”, a symbol transition between “+ y” and “−y”, and a transition between “+ z” and “−z”. It is a symbol transition. Specifically, when the signal TxF is “1”, transition is made so as to change the polarity of the symbol (for example, from “+ x” to “−x”), and when the signal TxF is “0”. Does not make such a transition.

  When the signal TxF is "0", the signals TxR and TxP are between "+ x" and other than "+ x", between "+ y" and "+ y", and between "+ z" and "+ z". Symbols are transitioned between. Specifically, when the signal TxR is "1" and the signal TxP is "0", the polarity of the symbol is maintained and clockwise in FIG. 4 (for example, from "+ x" to "+ y"). When the signal TxR is “1” and the signal TxP is “1”, the polarity of the symbol is changed and the signal is rotated clockwise in FIG. 4 (for example, from “+ x” to “−y”). Transition to "). When the signal TxR is “0” and the signal TxP is “0”, the symbol polarity is maintained and the counterclockwise transition (for example, from “+ x” to “+ z”) in FIG. 4 is performed. However, when the signal TxR is “0” and the signal TxP is “1”, the polarity of the symbol is changed and the signal is rotated counterclockwise in FIG. 4 (for example, from “+ x” to “−z”). Transition.

  In this way, in the signal generator 11, the direction of symbol transition is specified by the signals TxF, TxR, and TxP. Therefore, the signal generator 11 can determine the next symbol NS based on the current symbol CS and these signals TxF, TxR, and TxP. Then, the signal generator 11 supplies the symbol NS to the flip-flop 13 by using the 3-bit signal S1 in this example.

  The signal generator 11 also has a function of generating the signals EA, EB, and EC based on the LUT (Look Up Table) 19 supplied from the register 12. The signal EA indicates whether to perform pre-emphasis on the signal SIGA, and the signal generation unit 11 controls the signal SIGA to perform pre-emphasis by activating the signal EA. Similarly, the signal EB indicates whether or not to perform pre-emphasis on the signal SIGB, and the signal generator 11 activates the signal EB to control to perform pre-emphasis on the signal SIGB. To do. Further, the signal EC indicates whether or not to perform pre-emphasis on the signal SIGC, and the signal generation unit 11 makes the signal EC active so as to perform pre-emphasis on the signal SIGC. . The LUT 19 shows the relationship between the current symbol CS, the signals TxF, TxR, TxP, and the signals EA, EB, EC. The signal generation unit 11 refers to the LUT 19 based on the current symbol CS and the signals TxF, TxR, TxP and generates signals EA, EB, EC. In other words, the signal generation unit 11 generates the signals EA, EB, and EC according to two symbols (the current symbol CS and the next symbol NS) that are temporally adjacent to each other, that is, two consecutive symbols. Has become.

  With this configuration, the signal generation unit 11 can selectively perform pre-emphasis on some transitions among the transitions among the voltage states SH, SM, and SL, and the signals SIGA, SIGB, and Pre-emphasis can be selectively performed on some signals of the SIGC.

  The register 12 stores the LUT 19. The LUT 19 is written in the register 12 by an application processor (not shown) when the power of the transmitter 10 is turned on, for example.

  The flip-flop 13 delays the signal S1 by one clock of the clock TxCK and outputs it as a 3-bit signal S2. That is, the flip-flop 13 generates the current symbol CS by delaying the next symbol NS indicated by the signal S1 by one clock of the clock TxCK. Then, the flip-flop 13 supplies the signal S2 to the signal generator 11 and the transmitter 20.

  The flip-flop 14 delays the signals EA, EB, and EC by one clock of the clock TxCK and outputs the delayed signals. The flip-flop 15 delays the three output signals of the flip-flop 14 by one clock TxCK and outputs the delayed signals as signals EA2, EB2, and EC2, respectively. Then, the flip-flop 15 supplies the signals EA2, EB2, EC2 to the transmitter 20.

  The transmitter 20 generates signals SIGA, SIGB, SIGC based on the signal S2 and the signals EA2, EB2, EC2.

  FIG. 5 illustrates a configuration example of the transmission unit 20. The transmission unit 20 includes an output control unit 21, output units 22A, 22B and 22C, an emphasis control unit 23, and output units 24A, 24B and 24C.

  The output control unit 21 supplies a control signal to the output units 22A, 22B, 22C based on the signal S2 to control the operation of the output units 22A, 22B, 22C.

  The output unit 22A sets the voltage state of the signal SIGA to one of the voltage states SH, SM, SL based on the control signal supplied from the output control unit 21. The output unit 22B sets the voltage state of the signal SIGB to one of the voltage states SH, SM, SL based on the control signal supplied from the output control unit 21. The output unit 22C sets the voltage state of the signal SIGC to one of the voltage states SH, SM, SL based on the control signal supplied from the output control unit 21.

  With this configuration, the transmitter 20 sets the signals SIGA, SIGB, and SIGC to the voltage states SH, SM, and SL corresponding to the symbol CS, as shown in FIG. 2, based on the symbol CS indicated by the signal S2. Is able to.

  Hereinafter, the output unit 22A of the transmission unit 20 will be described in more detail. The same applies to the output units 22B and 22C.

  The output unit 22A includes transistors 25 and 26 and resistance elements 27 and 28. In this example, the transistors 25 and 26 are N-channel MOS (Metal Oxide Semiconductor) type FETs (Field Effect Transistors). A control signal is supplied to the gate of the transistor 25 from the output control unit 21, the voltage V1 is supplied to the drain, and the source is connected to one end of the resistance element 27. A control signal is supplied from the output control unit 21 to the gate of the transistor 26, the drain is connected to one end of the resistance element 28, and the source is grounded. The resistance elements 27 and 28 function as terminating resistors in the communication system 1. One end of the resistance element 27 is connected to the source of the transistor 25, the other end is connected to the other end of the resistance element 28, and is also connected to the output terminal ToutA. One end of the resistance element 28 is connected to the drain of the transistor 26, the other end is connected to the other end of the resistance element 27, and is also connected to the output terminal ToutA.

  For example, when the signal SIGA is set to the voltage state SH, the output control unit 21 supplies a high level control signal to the transistor 25 and a low level control signal to the transistor 26. As a result, the transistor 25 is turned on and the transistor 26 is turned off, an output current flows through the transistor 25, and the signal SIGA is set to the voltage state SH. Further, for example, when the signal SIGA is set to the voltage state SL, the output control unit 21 supplies the low level control signal to the transistor 25 and the high level control signal to the transistor 26. As a result, the transistor 25 is turned off and the transistor 26 is turned on, an output current flows through the transistor 26, and the signal SIGA is set to the voltage state SL. Further, for example, when the signal SIGA is set to the voltage state SM, the output control unit 21 supplies a low level control signal to the transistors 25 and 26. As a result, the transistors 25, 26 are turned off, and the resistance elements 31A, 31B, 31C (described later) of the receiver 30 set the signal SIGA to the voltage state SM.

  The emphasis control unit 23 controls the operation of the output units 24A, 24B, 24C based on the signal S2 and the signals EA2, EB2, EC2. Specifically, the emphasis control unit 23 supplies a control signal to the output unit 24A based on the signal S2 and the signal EA2, and outputs a control signal to the output unit 24B based on the signal S2 and the signal EB2. The control signal is supplied to the output section 24C based on the signal S2 and the signal EC2.

  The output unit 24A performs pre-emphasis on the signal SIGA based on the control signal supplied from the emphasis control unit 23. The output unit 24B performs pre-emphasis on the signal SIGB based on the control signal supplied from the emphasis control unit 23. The output unit 24C performs pre-emphasis on the signal SIGC based on the control signal supplied from the emphasis control unit 23. The configurations of the output units 24A, 24B and 24C are similar to those of the output units 22A, 22B and 22C.

  With this configuration, the transmission unit 20 performs pre-emphasis on the signal SIGA when the signal EA2 is active, and performs pre-emphasis on the signal SIGB when the signal EB2 is active so that the signal EC2 becomes When active, the signal SIGC is pre-emphasized.

  The transmitting unit 20 is not limited to this configuration, and various other configurations can be applied.

  FIG. 6 illustrates a configuration example of the receiving device 30. The reception device 30 includes resistance elements 31A, 31B, 31C, amplifiers 32A, 32B, 32C, a clock generation unit 33, flip-flops (F / F) 34, 35, and a signal generation unit 36. .

  The resistance elements 31A, 31B, 31C function as terminating resistors in the communication system 1. One end of the resistance element 31A is connected to the input terminal TinA and is supplied with the signal SIGA, and the other end is connected to the other ends of the resistance elements 31B and 31C. One end of the resistance element 31B is connected to the input terminal TinB and is supplied with the signal SIGB, and the other end is connected to the other ends of the resistance elements 31A and 31C. One end of the resistance element 31C is connected to the input terminal TinC and the signal SIGC is supplied, and the other end is connected to the other ends of the resistance elements 31A and 31B.

  Each of the amplifiers 32A, 32B, and 32C outputs a signal corresponding to the difference between the signal at the positive input terminal and the signal at the negative input terminal. The positive input terminal of the amplifier 32A is connected to the negative input terminal of the amplifier 32C and one end of the resistance element 31A and is supplied with the signal SIGA, and the negative input terminal is connected to the positive input terminal of the amplifier 32B and one end of the resistance element 31B. At the same time, the signal SIGB is supplied. The positive input terminal of the amplifier 32B is connected to the negative input terminal of the amplifier 32A and one end of the resistance element 31B and is supplied with the signal SIGB, and the negative input terminal is connected to the positive input terminal of the amplifier 32C and one end of the resistance element 31C. At the same time, the signal SIGC is supplied. The positive input terminal of the amplifier 32C is connected to the negative input terminal of the amplifier 32B and one end of the resistance element 31C and is supplied with the signal SIGC, and the negative input terminal is connected to the positive input terminal of the amplifier 32A and one end of the resistance element 31A. At the same time, the signal SIGA is supplied.

  With this configuration, the amplifier 32A outputs a signal corresponding to the difference AB (SIGA-SIGB) between the signal SIGA and the signal SIGB, and the amplifier 32B responds to the difference BC (SIGB-SIGC) between the signal SIGB and the signal SIGC. The amplifier 32C outputs a signal corresponding to the difference CA (SIGC-SIGA) between the signal SIGC and the signal SIGA.

  FIG. 7 shows an operation example of the amplifiers 32A, 32B and 32C. In this example, the signal SIGA is the high level voltage VH, the signal SIGB is the low level voltage VL, and the signal SIGC is the medium level voltage VM. In this case, the current Iin flows in the order of the input terminal TinA, the resistance element 31A, the resistance element 31B, and the input terminal TinB. Then, the high-level voltage VH is supplied to the positive input terminal of the amplifier 32A and the low-level voltage VL is supplied to the negative input terminal, and the difference AB becomes positive (AB> 0). Is output. Further, the low-level voltage VL is supplied to the positive input terminal of the amplifier 32B and the medium-level voltage VM is supplied to the negative input terminal, and the difference BC becomes negative (BC <0). Is output. Further, since the positive input terminal of the amplifier 32C is supplied with the medium level voltage VM and the negative input terminal thereof is supplied with the high level voltage VH, the difference CA becomes negative (CA <0). "Is output.

  The clock generation unit 33 generates the clock RxCK based on the output signals of the amplifiers 32A, 32B, 32C.

  The flip-flop 34 delays the output signals of the amplifiers 32A, 32B, and 32C by one clock of the clock RxCK and outputs the delayed signals. That is, the output signal of the flip-flop 34 indicates the current symbol CS2. Here, the current symbol CS2 is one of the six symbols “+ x”, “−x”, “+ y”, “−y”, “+ z”, and “−z”, like the symbols CS and NS. It only shows one.

  The flip-flop 35 delays the three output signals of the flip-flop 34 by one clock RxCK and outputs the delayed signals. That is, the flip-flop 35 generates the symbol PS2 by delaying the current symbol CS2 by one clock of the clock RxCK. This symbol PS2 is the previously received symbol (previous symbol), and like the symbols CS, NS, CS2, the six symbols "+ x", "-x", "+ y", "-y", " It indicates either one of + z "and" -z ".

  The signal generator 36 generates signals RxF, RxR, and RxP based on the output signals of the flip-flops 34 and 35 and the clock RxCK. The signals RxF, RxR, and RxP correspond to the signals TxF, TxR, and TxP in the transmitter 10, respectively, and represent symbol transitions. The signal generation unit 36 identifies the transition of the symbol (FIG. 4) based on the current symbol CS2 indicated by the output signal of the flip-flop 34 and the previous symbol PS2 indicated by the output signal of the flip-flop 35, and the signal RxF, RxR and RxP are generated.

  Here, the transmission device 10 corresponds to a specific but not limitative example of “transmission device” in one embodiment of the present disclosure. The register 12 and the signal generation unit 11 correspond to a specific but not limitative example of “transmission control unit” in one embodiment of the present disclosure. The signals SIGA, SIGB, and SIGC correspond to a specific example of “one or more transmission signals” in the present disclosure.

[Operation and action]
Subsequently, the operation and action of the communication system 1 of the present embodiment will be described.

(Overview of overall operation)
First, the overall operation outline of the communication system 1 will be described with reference to FIG. In the transmitter 10, the signal generator 11 obtains the next symbol NS based on the current symbol CS and the signals TxF, TxR, and TxP, and outputs it as the signal S1. The signal generator 11 also refers to the LUT 19 based on the current symbol CS and the signals TxF, TxR, TxP to generate and output the signals EA, EB, EC. The flip-flop 13 delays the signal S1 by one clock of the clock TxCK and outputs it as a signal S2. The flip-flop 14 delays the signals EA, EB, and EC by one clock of the clock TxCK and outputs the delayed signals. The flip-flop 15 delays the three output signals of the flip-flop 14 by one clock of the clock TxCK and outputs the delayed signals as signals EA2, EB2 and EC2, respectively. The transmission unit 20 generates signals SIGA, SIGB, SIGC based on the signal S2 and the signals EA2, EB2, EC2.

  In the receiving device 30, the amplifier 32A outputs a signal according to the difference AB between the signal SIGA and the signal SIGB, the amplifier 32B outputs a signal according to the difference BC between the signal SIGB and the signal SIGC, and the amplifier 32C , And outputs a signal according to the difference CA between the signal SIGC and the signal SIGA. The clock generation unit 33 generates the clock RxCK based on the output signals of the amplifiers 32A, 32B, 32C. The flip-flop 34 delays the output signals of the amplifiers 32A, 32B and 32C by one clock of the clock RxCK and outputs the delayed signals. The flip-flop 35 delays the three output signals of the flip-flop 34 by one clock RxCK and outputs the delayed signals. The signal generator 36 generates signals RxF, RxR, and RxP based on the output signals of the flip-flops 34 and 35 and the clock RxCK.

(Detailed operation)
The signal generation unit 11 obtains the next symbol NS based on the current symbol CS and the signals TxF, TxR, and TxP, and also refers to the LUT 19 to determine whether to perform pre-emphasis on the signals SIGA, SIGB, and SIGC. The signals EA, EB, and EC shown are generated.

  FIG. 8 shows an example of the LUT 19, and shows the relationship between the current symbol CS, the signals TxF, TxR, TxP, and the signals EA, EB, EC. Note that, in FIG. 8, the following symbol NS is also shown for convenience of description.

  The signal generation unit 11 refers to the LUT 19 based on the current symbol CS and the signals TxF, TxR, TxP and generates signals EA, EB, EC. Then, the flip-flops 14 and 15 delay the signals EA, EB, and EC to generate the signals EA2, EB2, and EC2, and the transmitter 20 receives the signals SIGA and SIGB based on the signals EA2, EB2, and EC2. , SIGC is pre-emphasized. Hereinafter, a case where the current symbol CS is “+ x” and a case where the current symbol CS is “−x” will be described in detail as an example.

  9A to 9E and 10A to 10E show the operation when the symbol transits from "+ x" to other than "+ x", and FIGS. 9A to 9E show the waveforms of the signals SIGA, SIGB, and SIGC. 10A to 10E show waveforms of the differences AB, BC, CA. 9A and 10A show a transition from “+ x” to “−x”, FIGS. 9B and 10B show a transition from “+ x” to “+ y”, and FIGS. 9C and 10C show “+ x” to “−y”. 9D and 10D show the transition from “+ x” to “+ z”, and FIGS. 9E and 10E show the transition from “+ x” to “−z”. Further, in FIGS. 9A to 9E and 10A to 10E, thin lines indicate the case where pre-emphasis is not performed, and thick lines indicate the case where pre-emphasis is performed. In this example, the lengths of the transmission lines 9A to 9C are sufficiently short.

  When the symbol transits from “+ x” to “−x”, the signal generator 11 sets the signals EA, EB, and EC to “1”, “1”, and “0”, as shown in FIG. To do. As a result, as shown in FIG. 9A, the transmitter 20 performs pre-emphasis on the signal SIGA to make a transition from the high level voltage VH to a voltage lower than the low level voltage VL, and to the signal SIGB. Pre-emphasis is performed to make a transition from the low level voltage VL to a voltage higher than the high level voltage VH. At this time, the transmission unit 20 does not perform pre-emphasis on the signal SIGC and maintains the medium level voltage VM. As a result, as shown in FIG. 10A, the difference AB transits from the positive voltage to the negative voltage earlier than in the case where pre-emphasis is not performed, and the difference BC, CA is when pre-emphasis is not performed. Transition from negative to positive faster than.

  When the symbol transits from "+ x" to "+ y", the signal generator 11 sets the signals EA, EB, EC to "0", "1", "1", as shown in FIG. . As a result, the transmitter 20 performs pre-emphasis on the signal SIGB as shown in FIG. 9B, transitions from the low level voltage VL to a voltage higher than the high level voltage VH, and responds to the signal SIGC. Pre-emphasis is performed, and the medium level voltage VM is changed to a voltage lower than the low level voltage VL. At this time, the transmission unit 20 does not perform pre-emphasis on the signal SIGA, and makes a transition from the high level voltage VH to the middle level voltage VM. That is, the signal SIGA transitions from the voltage state SH to the voltage state SM, but the transmitter 20 does not perform pre-emphasis on the signal SIGA. As a result, as shown in FIG. 10B, the difference AB transits from positive to negative faster than in the case where pre-emphasis is not performed, and the difference BC is negative in comparison with the case where pre-emphasis is not performed. Transition to positive faster. Further, the difference CA maintains the negative state.

  When the symbol transits from "+ x" to "-y", the signal generator 11 sets the signals EA, EB, and EC to "0", "1", and "1", as shown in FIG. To do. As a result, the transmitter 20 performs pre-emphasis on the signal SIGB as shown in FIG. 9C, transitions from the low level voltage VL to a voltage lower than the low level voltage VL, and at the same time with respect to the signal SIGC. Pre-emphasis is performed, and the intermediate level voltage VM is changed to a voltage higher than the high level voltage VH. That is, the signal SIGB maintains the voltage state SL, but the transmitter 20 performs pre-emphasis on the signal SIGB. At this time, the transmission unit 20 does not perform pre-emphasis on the signal SIGA, but makes a transition from the high level voltage VH to the middle level voltage VM. That is, the signal SIGA transitions from the voltage state SH to the voltage state SM, but the transmitter 20 does not perform pre-emphasis on the signal SIGA. As a result, as shown in FIG. 10C, the difference CA changes from negative pressure to positive pressure earlier than in the case where pre-emphasis is not performed. Further, the difference AB maintains the positive state, and the difference BC maintains the negative state.

  When the symbol transits from "+ x" to "+ z", the signal generator 11 sets the signals EA, EB, EC to "1", "0", "1" as shown in FIG. . As a result, the transmission unit 20 performs pre-emphasis on the signal SIGA, transitions from the high level voltage VH to a voltage lower than the low level voltage VL, as shown in FIG. 9D, and responds to the signal SIGC. Pre-emphasis is performed, and the intermediate level voltage VM is changed to a voltage higher than the high level voltage VH. At this time, the transmission unit 20 does not perform pre-emphasis on the signal SIGB, but makes a transition from the low level voltage VL to the middle level voltage VM. That is, the signal SIGB transits from the voltage state SL to the voltage state SM, but the transmitter 20 does not perform pre-emphasis on the signal SIGB. As a result, as shown in FIG. 10D, the difference AB makes a transition from positive to negative faster than in the case where pre-emphasis is not performed, and the difference CA is negative in comparison with the case where pre-emphasis is not performed. Transition to positive faster. Moreover, the difference BC maintains a negative state.

  When the symbol transits from “+ x” to “−z”, the signal generator 11 changes the signals EA, EB, and EC to “1”, “0”, and “1”, as shown in FIG. To do. As a result, the transmission unit 20 performs pre-emphasis on the signal SIGA, transitions from the high level voltage VH to a voltage higher than the high level voltage VH, and responds to the signal SIGC as illustrated in FIG. 9E. Pre-emphasis is performed, and the medium level voltage VM is changed to a voltage lower than the low level voltage VL. That is, the signal SIGA maintains the voltage state SH, but the transmitter 20 performs pre-emphasis on the signal SIGA. At this time, the transmission unit 20 does not perform pre-emphasis on the signal SIGB, but makes a transition from the low level voltage VL to the middle level voltage VM. That is, the signal SIGB transits from the voltage state SL to the voltage state SM, but the transmitter 20 does not perform pre-emphasis on the signal SIGB. As a result, as shown in FIG. 10E, the difference BC makes a transition from negative to positive earlier than in the case where pre-emphasis is not performed. Further, the difference AB maintains the positive state, and the difference CA maintains the negative state.

  11A to 11E and 12A to 12E show the operation when the symbol transits from "-x" to other than "-x", and FIGS. 11A to 11E show the waveforms of the signals SIGA, SIGB, and SIGC. 12A to 12E show waveforms of the differences AB, BC, CA. 11A and 12A show a transition from “−x” to “+ x”, FIGS. 11B and 12B show a transition from “−x” to “+ y”, and FIGS. 11C and 12C show “−x” to “−”. 11D and 12D show the transition from “−x” to “+ z”, and FIGS. 11E and 12E show the transition from “−x” to “−z”.

  When the symbol transits from "-x" to "+ x", the signal generator 11 sets the signals EA, EB, and EC to "1", "1", and "0", as shown in FIG. To do. As a result, the transmission unit 20 performs pre-emphasis on the signal SIGA to cause the signal SIGA to transition from the low level voltage VL to a voltage higher than the high level voltage VH, and to the signal SIGB, as shown in FIG. 11A. Pre-emphasis is performed to transition the high level voltage VH to a voltage lower than the low level voltage VL. At this time, the transmission unit 20 does not perform pre-emphasis on the signal SIGC and maintains the medium level voltage VM. As a result, as shown in FIG. 12A, the difference AB makes a transition from negative to positive faster than in the case where pre-emphasis is not performed, and the difference BC, CA is compared to the case where pre-emphasis is not performed. Faster transition from positive to negative.

  When the symbol transits from "-x" to "+ y", the signal generator 11 sets the signals EA, EB, and EC to "0", "1", and "1", as shown in FIG. To do. As a result, the transmission unit 20 performs pre-emphasis on the signal SIGB as shown in FIG. 11B, transitions from the high level voltage VH to a voltage higher than the high level voltage VH, and with respect to the signal SIGC. Pre-emphasis is performed, and the medium level voltage VM is changed to a voltage lower than the low level voltage VL. That is, the signal SIGB maintains the voltage state SH, but the transmitter 20 performs pre-emphasis on the signal SIGB. At this time, the transmission unit 20 does not perform pre-emphasis on the signal SIGA and transitions from the low level voltage VL to the intermediate level voltage VM. That is, the signal SIGA transits from the voltage state SL to the voltage state SM, but the transmitter 20 does not perform pre-emphasis on the signal SIGA. As a result, as shown in FIG. 12B, the difference CA transits from positive to negative faster than in the case where pre-emphasis is not performed. Further, the difference BC maintains the positive state, and the difference AB maintains the negative state.

  When the symbol transits from "-x" to "-y", the signal generator 11 sets the signals EA, EB, and EC to "0", "1", "1", as shown in FIG. To As a result, the transmitter 20 performs pre-emphasis on the signal SIGB as shown in FIG. 11C, transitions the high-level voltage VH to a voltage lower than the low-level voltage VL, and responds to the signal SIGC. Pre-emphasis is performed, and the intermediate level voltage VM is changed to a voltage higher than the high level voltage VH. At this time, the transmission unit 20 does not perform pre-emphasis on the signal SIGA, but makes a transition from the low level voltage VL to the intermediate level voltage VM. That is, the signal SIGA transits from the voltage state SL to the voltage state SM, but the transmitter 20 does not perform pre-emphasis on the signal SIGA. As a result, as shown in FIG. 12C, the difference AB transits from negative to positive more quickly than in the case without pre-emphasis, and the difference BC changes from positive to positive in comparison with the case without pre-emphasis. Transition to negative faster. Further, the difference CA maintains the positive state.

  When the symbol transits from "-x" to "+ z", the signal generator 11 sets the signals EA, EB, and EC to "1", "0", and "1", as shown in FIG. To do. As a result, the transmission unit 20 performs pre-emphasis on the signal SIGA to cause the signal SIGA to transition from the low level voltage VL to a voltage lower than the low level voltage VL, as shown in FIG. 11D, and to the signal SIGC. Pre-emphasis is performed, and the intermediate level voltage VM is changed to a voltage higher than the high level voltage VH. That is, the signal SIGA maintains the voltage state SL, but the transmitter 20 performs pre-emphasis on the signal SIGA. At this time, the transmission unit 20 does not perform pre-emphasis on the signal SIGB, but makes a transition from the high level voltage VH to the middle level voltage VM. That is, the signal SIGB transits from the voltage state SH to the voltage state SM, but the transmitter 20 does not perform pre-emphasis on this signal SIGB. As a result, as shown in FIG. 12D, the difference BC transits from positive to negative faster than in the case where pre-emphasis is not performed. Further, the difference AB maintains the negative state, and the difference CA maintains the positive state.

  When the symbol transitions from "-x" to "-z", the signal generator 11 sets the signals EA, EB, and EC to "1", "0", and "1", as shown in FIG. To As a result, the transmission unit 20 performs pre-emphasis on the signal SIGA to cause the signal SIGA to transition from the low level voltage VL to a voltage higher than the high level voltage VH, as shown in FIG. 11E, and to the signal SIGC. Pre-emphasis is performed, and the medium level voltage VM is changed to a voltage lower than the low level voltage VL. At this time, the transmission unit 20 does not perform pre-emphasis on the signal SIGB, but makes a transition from the high level voltage VH to the middle level voltage VM. That is, the signal SIGB transits from the voltage state SH to the voltage state SM, but the transmitter 20 does not perform pre-emphasis on this signal SIGB. As a result, as shown in FIG. 12E, the difference AB transits from negative to positive more quickly than in the case without pre-emphasis, and the difference CA changes from positive to positive in comparison with the case without pre-emphasis. Transition to negative faster. In addition, the difference BC maintains the positive state.

  In this way, the transmission device 10 performs pre-emphasis on the signal of the signals SIGA to SIGC that transitions from the voltage states SL and SM to the voltage state SH, and transitions from the voltage states SH and SM to the voltage state SL. Performs pre-emphasis on the signal. Further, the transmission device 10 also performs pre-emphasis on the signal that maintains the voltage states SL and SH among the signals SIGA to SIGC. On the other hand, the transmission device 10 does not perform pre-emphasis on a signal of the signals SIGA to SIGC that transits from the voltage states SL and SH to the voltage state SM, and also on a signal that maintains the voltage state SM. No pre-emphasis.

  The amplifiers 32A to 32C generate and output signals according to whether the differences AB, BC, and CA are positive or negative. Therefore, in this communication system 1, the jitter TJ is defined by the deviation width of the timing at which the differences AB, BC, CA cross “0” as shown in FIGS. 10A to 10E and 12A to 12E. In the communication system 1, since pre-emphasis is performed on the signals SIGA to SIGC, the transition of the signal becomes steep, so that the jitter TJ can be reduced. In particular, when the transition from the symbol "+ x" to "+ y" (Fig. 10B) or the transition from the symbol "+ x" to "+ z" (Fig. 10D) occurs, two of the differences AB, BC, CA are ". In the case of straddling 0 ″, the jitter TJ can be effectively improved.

  Next, some of the symbol transitions will be taken as examples to describe in more detail.

  First, the case where the symbol transits from “+ x” to “+ y” will be described. In this case, as shown in FIG. 9B, the signal SIGA transitions from the voltage state SH (for example, the high level voltage VH) to the voltage state SM (for example, the medium level voltage VM), and the signal SIGB changes to the voltage state SL (for example, the low state). The level voltage VL) changes to the voltage state SH, and the signal SIGC changes from the voltage state SM to the voltage state SL. In this case, as shown in FIG. 10B, for example, the transition time of the difference AB becomes long. The first cause is that the signal SIGA transitions to the medium level voltage VM. That is, when the signal SIGA is set to the medium level voltage VM, the output unit 22A of the transmission unit 20 turns off both the transistors 25 and 26. That is, the signal SIGA is set to the voltage state SM by the resistance elements 31A to 31C of the receiving device 30. As a result, the transition time of the signal SIGA becomes long and the transition time of the difference AB also becomes long. The second cause is that the voltage change amount of the difference AB is large.

  Such a case also occurs, for example, when the symbol transits from "+ x" to "+ z" (FIGS. 9D and 10D). In this case, as shown in FIG. 9D, the signal SIGA transits from the voltage state SH (for example, the high level voltage VH) to the voltage state SL (for example, the low level voltage VL), and the signal SIGB changes from the voltage state SL to the voltage state. The transition to SM (for example, the medium level voltage VM) and the signal SIGC transitions from the voltage state SM to the voltage state SH. In addition, it also occurs when the symbol transits from "-x" to "-y" (Figs. 11C and 12C) and when the symbol transits from "-x" to "-z" (Figs. 11E and 12E).

  13 and 14 show the operation when the symbol transits from "+ x" to "+ y", and FIGS. 13A to 13C show the waveforms of the signals SIGA, SIGB, and SIGC, respectively. 14A to 14C show waveforms of the differences AB, BC, and CA, respectively. FIG. 13 corresponds to FIG. 9B, and FIG. 14 corresponds to FIG. 10B. FIG. 14 also shows an eye mask EM indicating the reference of the eye opening.

  When the symbol transits from “+ x” to “+ y”, the transmitter 20 enhances the transition of the signal SIGB by the voltage ΔV and the transition of the signal SIGC by the voltage ΔV, as shown in FIG. 13. At this time, the difference AB becomes like the waveform W1 of FIG. 14, and the difference BC becomes like the waveform W3 of FIG. In this way, in the communication system 1, pre-emphasis is performed to make the transition of the waveform steep, so that the eye can be widened. If pre-emphasis is not performed on the signals SIGA to SIGC, for example, the difference AB has a waveform W2 in FIG. 14 and the difference BC has a waveform W4 in FIG. That is, in such a case, since the transition of the waveform becomes dull and the amplitude of the difference becomes small, the eye may become narrow. On the other hand, in the communication system 1, since pre-emphasis is performed on the signals SIGA to SIGC, the eye can be widened and the communication quality can be improved.

  Next, a case where the symbol transits from “+ x” to “−z” will be described.

  15 and 16 show the operation when the symbol transits from "+ x" to "-z", and FIGS. 15A to 15C show the waveforms of the signals SIGA, SIGB, and SIGC, respectively. 16A to 16C show waveforms of the differences AB, BC, and CA, respectively. FIG. 15 corresponds to FIG. 9E, and FIG. 16 corresponds to FIG. 10E.

  When the symbol makes a transition from “+ x” to “−z”, the transmission unit 20 sets the voltage of the signal SIGA to a voltage higher by the voltage ΔV and makes the transition of the signal SIGC become the voltage ΔV as shown in FIG. Just emphasize. That is, the transmission unit 20 performs pre-emphasis on the signal SIGA even though the signal SIGA maintains the voltage state SH, and the signal SIGB transitions from the voltage state SL to the voltage state SM. , The signal SIGB is not pre-emphasized. In other words, the transmitter 10 selects the signals SIGA and SIGC and performs pre-emphasis on them. At this time, the difference AB becomes like the waveform W11 of FIG. 16, and the difference BC becomes like the waveform W13 of FIG. In this way, in the communication system 1, pre-emphasis is performed to make the transition of the waveform steep, so that the eye can be widened. If the signals SIGA to SIGC are not pre-emphasized, for example, the difference AB has a waveform W12 in FIG. 16 and the difference BC has a waveform W14 in FIG. That is, in such a case, since the transition of the waveform becomes dull and the amplitude of the difference becomes small, the eye may become narrow. On the other hand, in the communication system 1, since pre-emphasis is performed on the signals SIGA to SIGC, the eye can be widened and the communication quality can be improved.

[Comparative example]
Here, as a comparative example, of the signals SIGA to SIGC, a case will be examined in which pre-emphasis is performed on a signal having a voltage state transition and pre-emphasis is not performed on a signal having no voltage state transition.

  17 and 18 show the operation when the symbol transits from "+ x" to "-z", and FIGS. 17A to 17C show the waveforms of the signals SIGA, SIGB and SIGC, respectively. 18A to 18C show waveforms of the differences AB, BC, and CA, respectively.

  When the symbol makes a transition from “+ x” to “−z”, the transmitter 10R according to the comparative example emphasizes the transition of the signal SIGB by the voltage ΔV and changes the transition of the signal SIGC to the voltage as shown in FIG. Emphasize only ΔV. That is, pre-emphasis is performed on the signals SIGB and SIGC whose voltage states change, and pre-emphasis is not performed on the signal SIGA whose voltage state does not change. At this time, the difference AB becomes as shown in FIG. 18A, and the eye may be narrowed.

  On the other hand, in the communication system 1, the signal for pre-emphasis is selected from the signals SIGA to SIGC. Specifically, as shown in FIG. 15, the transmitter 10 according to the present embodiment sets the voltage of the signal SIGA to a voltage higher by the voltage ΔV and emphasizes the transition of the signal SIGC by the voltage ΔV. That is, the transmitter 10 performs pre-emphasis on the signal SIGA even though the signal SIGA maintains the voltage state SH, and the signal SIGB transitions from the voltage state SL to the voltage state SM. , The signal SIGB is not pre-emphasized. As a result, in the communication system 1, it is possible to reduce the possibility that the eye becomes narrower and improve the communication quality.

  As described above, in the communication system 1, since the pre-emphasis is selectively performed on the signals SIGA to SIGC, for example, when the transition has a large jitter, the pre-emphasis is performed and the pre-emphasis is performed. If the transition is such that N is narrowed, pre-emphasis can be omitted. Thereby, the communication quality can be improved in the communication system 1.

[effect]
As described above, in the present embodiment, the preemphasis is selectively performed on the signals SIGA to SIGC, so that the communication quality can be improved.

[Modification 1-1]
In the above embodiment, as shown in FIG. 8, pre-emphasis is performed on at least one of the signals SIGA, SIGB, and SIGC at any transition between the six symbols, but the present invention is not limited to this. It is not something that will be done. Instead of this, for example, pre-emphasis may be performed on only some of the transitions between the six symbols. The communication system 1A according to this modification will be described below in detail.

  FIG. 19 shows an example of an LUT 19A according to this modification. The signal generation unit 11A according to the present modification generates the signals EA, EB, EC based on the LUT 19A. The signal generation unit 11A, for example, when the symbol transits from “+ x” to “−x”, when the symbol transits from “+ x” to “−y”, and when the symbol transits from “+ x” to “−z”. When making a transition, all the signals EA, EB, and EC are set to "0". That is, in these cases, the transmission unit 20 does not perform pre-emphasis on any of the signals SIGA, SIGB, and SIGC. For example, in the case where the symbol transitions from "+ x" to "-z", for example, if pre-emphasis is performed as shown in FIGS. 17 and 18, the eye becomes narrower. Does not perform pre-emphasis. On the other hand, the signal generation unit 11A sets the signals EA, EB, and EC to "0", "1", and "1" when the symbol changes from "+ x" to "+ y", and the symbol changes to "1". When transitioning from "+ x" to "+ z", the signals EA, EB, and EC are set to "1", "0", "1". That is, in these cases, as shown in FIGS. 10B and 10D, since the transition time of the difference AB becomes long, the transmission unit 20 performs pre-emphasis. There are two cases in which pre-emphasis is performed in this way. That is, one of the signals SIGA, SIGB, and SIGC is that the first signal transits from the voltage state SH (for example, high level voltage VH) to the voltage state SM (for example, medium level voltage VM), and the second signal Is a case in which the voltage state SL (for example, the low level voltage VL) transits to the voltage state SH, and the third signal transits from the voltage state SM to the voltage state SL. And, the other is that among the signals SIGA, SIGB, SIGC, the first signal transits from the voltage state SL to the voltage state SM, and the second signal transits from the voltage state SH to the voltage state SL. In this case, the signal of No. 3 transits from the voltage state SM to the voltage state SH. In other words, it is a case where all of the voltage state of the signal SIGA, the voltage state of the signal SIGB, and the voltage state of the signal SIGC make a transition. As described above, in the communication system 1A, the pre-emphasis is performed only when one of the transition times of the differences AB, BC, CA becomes long, and the pre-emphasis is not performed in other cases. Even with this configuration, the same effect as that of the communication system 1 according to the above-described embodiment can be obtained.

  Note that, among the transitions among the six symbols, the transition for which pre-emphasis is performed is not limited to the example of FIG. 19, and it is possible to arbitrarily set which transition to perform pre-emphasis.

[Modification 1-2]
In the above-described embodiment, the signal generator 11 generates the three signals EA, EB, and EC and independently controls the pre-emphasis for the signals SIGA to SIGC, but the present invention is not limited to this. Absent. Below, the transmitter 10B which concerns on this modification is demonstrated in detail.

  FIG. 20 illustrates a configuration example of the transmission device 10B. The transmitter 10B includes a signal generator 11B, flip-flops 14B and 15B, and a transmitter 20B. The signal generator 11B is for obtaining the next symbol NS based on the current symbol CS and the signals TxF, TxR, TxP, and for generating the signal EE by referring to the LUT 19B. The flip-flop 14B delays the signal EE by one clock of the clock TxCK and outputs it. The flip-flop 15B delays the output signal of the flip-flop 14 by one clock of the clock TxCK and outputs it as a signal EE2. The transmitter 20B generates signals SIGA, SIGB, and SIGC based on the signal S2 and the signal EE2. At that time, the transmitter 20B is configured to perform pre-emphasis on the signals SIGA, SIGB, and SIGC when the signal EE2 is active. With this configuration, in the transmission device 10B, the signal generation unit 11B collectively controls the pre-emphasis for the signals SIGA to SIGC.

  FIG. 21 shows an example of the LUT 19B according to this modification. The signal generation unit 11B, for example, when the symbol transits from “+ x” to “−x”, when the symbol transits from “+ x” to “−y”, and when the symbol transits from “+ x” to “−z”. When making a transition, the signal EE is set to "0". That is, in these cases, the transmitter 20B does not perform pre-emphasis on the signals SIGA, SIGB, and SIGC. On the other hand, the signal generation unit 11B sets the signal EE to "1" when the symbol transits from "+ x" to "+ y" and when the symbol transits from "+ x" to "+ z", for example. That is, in these cases, as in the case of the modification 1-1, the transition time of the difference AB becomes long, so that the transmission unit 20B performs pre-emphasis on the signals SIGA, SIGB, and SIGC. As described above, the transmission device 10B operates so as to perform pre-emphasis only when one of the transition times of the differences AB, BC, and CA becomes long, and does not perform pre-emphasis at other times. Even with this configuration, the same effect as that of the communication system 1 according to the above-described embodiment can be obtained.

  Note that, among the transitions among the six symbols, the transition for which pre-emphasis is performed is not limited to the example of FIG. 21, and which transition is to be subjected to pre-emphasis can be set arbitrarily. For example, the pre-emphasis may be performed only when any two of the differences AB, BC, and CA transit over "0". Further, for example, the pre-emphasis may be performed only when all of the differences AB, BC, and CA transit over “0”.

[Modification 1-3]
The operation of generating the signals EA, EB, and EC with reference to the LUT 19 by the signal generation unit 11 may be realized by software or hardware. The following is an example of a method implemented by hardware. Here, an example in which the present modification is applied to the signal generation unit 11B according to Modification 1-2 will be described.

  FIG. 22 illustrates a configuration example of a portion that generates the signal EE in the signal generation unit 11C according to this modification. In this example, the signal generator 11C generates the signal EE based on the current symbol CS, the next symbol NS, and the LUT 19B. The signal generation unit 11C includes symbol determination units 100 and 110, logic circuits 120, 130, 140, 150, 160 and 170, and a logical sum circuit 180.

  The symbol determination unit 100 determines which of the six symbols “+ x”, “−x”, “+ y”, “−y”, “+ z”, and “−z” is the current symbol CS. To do. The symbol determination unit 100 has comparison units 101 to 106. The comparison unit 101 outputs "1" when the current symbol CS is the symbol "+ x". The comparison unit 102 outputs "1" when the current symbol CS is the symbol "-x". The comparison unit 103 outputs "1" when the current symbol CS is the symbol "+ y". The comparison unit 104 outputs "1" when the current symbol CS is the symbol "-y". The comparison unit 105 outputs "1" when the current symbol CS is the symbol "+ z". The comparison unit 106 outputs "1" when the current symbol CS is the symbol "-z".

  The symbol determination unit 110 determines which of the six symbols “+ x”, “−x”, “+ y”, “−y”, “+ z”, and “−z” is the next symbol NS. To do. The symbol determination unit 110 has comparison units 111 to 116. The comparison unit 111 outputs "1" when the next symbol NS is the symbol "+ x". The comparison unit 112 outputs "1" when the next symbol NS is the symbol "-x". The comparison unit 113 outputs "1" when the next symbol NS is the symbol "+ y". The comparison unit 114 outputs "1" when the next symbol NS is the symbol "-y". The comparison unit 115 outputs "1" when the next symbol NS is the symbol "+ z". The comparing unit 116 outputs "1" when the next symbol NS is the symbol "-z".

  The logic circuit 120 generates a signal based on the output signal of the comparison unit 101, the output signals of the comparison units 112 to 116, and the pre-emphasis setting in the LUT 19B.

  The logic circuit 120 has AND circuits 121 to 125. The output signal of the comparison unit 101 is supplied to the first input terminal of the logical product circuit 121, the output signal of the comparison unit 112 is supplied to the second input terminal, and the third input terminal is included in the LUT 19B. The value (“0” in this example) of the signal EE corresponding to the symbol CS = “+ x” and the symbol NS = “− x” is supplied. That is, the comparison unit 101 outputs “1” when the current symbol CS is the symbol “+ x”, and the comparison unit 112 outputs “1” when the next symbol NS is the symbol “−x”. Since it outputs "1", the value of the signal EE corresponding to the symbol CS = "+ x" and the symbol NS = "-x" is supplied to the third input terminal. Similarly, the output signal of the comparison unit 101 is supplied to the first input terminal of the AND circuit 122, the output signal of the comparison unit 113 is supplied to the second input terminal, and the third input terminal is The value (“1” in this example) of the signal EE corresponding to the symbol CS = “+ x” and the symbol NS = “+ y” included in the LUT 19B is supplied. The output signal of the comparison unit 101 is supplied to the first input terminal of the logical product circuit 123, the output signal of the comparison unit 114 is supplied to the second input terminal, and the third input terminal is included in the LUT 19B. The value (“0” in this example) of the signal EE corresponding to the symbol CS = “+ x” and the symbol NS = “− y” is supplied. The output signal of the comparison unit 101 is supplied to the first input terminal of the AND circuit 124, the output signal of the comparison unit 115 is supplied to the second input terminal, and the third input terminal is included in the LUT 19B. The value of the signal EE (“1” in this example) corresponding to the symbol CS = “+ x” and the symbol NS = “+ z” is supplied. The output signal of the comparison unit 101 is supplied to the first input terminal of the AND circuit 125, the output signal of the comparison unit 116 is supplied to the second input terminal, and the third input terminal is included in the LUT 19B. The value (“0” in this example) of the signal EE corresponding to the symbol CS = “+ x” and the symbol NS = “− z” is supplied.

  As a result, in the logic circuit 120, as shown in FIG. 21, when the symbol CS = “+ x” and the symbol NS = “+ y”, the logical product circuit 122 outputs “1” and the symbol CS = “+ x” and When the symbol NS = “+ z”, the AND circuit 124 outputs “1”.

  Similarly, the logic circuit 130 generates a signal based on the output signal of the comparison unit 102, the output signals of the comparison units 111 and 113 to 116, and the pre-emphasis setting in the LUT 19B. The logic circuit 140 generates a signal based on the output signal of the comparison unit 103, the output signals of the comparison units 111, 112, 114 to 116, and the pre-emphasis setting in the LUT 19B. The logic circuit 150 generates a signal based on the output signal of the comparison unit 104, the output signals of the comparison units 111 to 113, 115 and 116, and the pre-emphasis setting in the LUT 19B. The logic circuit 160 generates a signal based on the output signal of the comparison unit 105, the output signals of the comparison units 111 to 114 and 116, and the pre-emphasis setting in the LUT 19B. The logic circuit 170 generates a signal based on the output signal of the comparison unit 106, the output signals of the comparison units 111 to 116, and the pre-emphasis setting in the LUT 19B. The logic circuits 130, 140, 150, 160 and 170 have the same configuration as the logic circuit 120.

  The logical sum circuit 180 calculates the logical sum of the output signals of all the logical product circuits in the logical circuits 120, 130, 140, 150, 160 and 170.

  Even with this configuration, the same effect as that of the communication system 1 according to the above-described embodiment can be obtained.

[Modification 1-4]
In the above-described embodiment, the transmission device 10 performs pre-emphasis on the signals SIGA, SIGB, and SIGC, but the present invention is not limited to this, and instead performs, for example, de-emphasis. May be. Below, the transmitter 10D which concerns on this modification is demonstrated in detail.

  FIG. 23 shows an example of the LUT 19D according to this modification. The signal generation unit 11D of the transmission device 10D refers to the LUT 19D based on the current symbol CS and the signals TxF, TxR, TxP and generates signals EA, EB, EC. Then, the transmitter 20D of the transmitter 10D performs deemphasis on the signals SIGA, SIGB, and SIGC based on the signals EA2, EB2, and EC2. Hereinafter, the case where the current symbol CS is “+ x” will be described in detail as an example.

  24A to 24E and 25A to 25E show the operation when the symbol transits from "+ x" to other than "+ x", and FIGS. 24A to 24E show the waveforms of the signals SIGA, SIGB, and SIGC. 25A to 25E show waveforms of the differences AB, BC, CA. In this example, the lengths of the transmission lines 9A to 9C are sufficiently short.

  When the symbol transits from "+ x" to "-x", the signal generator 11D sets the signals EA, EB, and EC to "0", "0", and "0", as shown in FIG. To do. As a result, the transmission unit 20D does not perform de-emphasis on the signals SIGA to SIGC as illustrated in FIG. 24A. As a result, the differences AB, BC, CA have the waveforms shown in FIG. 25A.

  When the symbol transits from "+ x" to "+ y", the signal generator 11D sets the signals EA, EB, and EC to "0", "0", "0", as shown in FIG. . As a result, the transmitter 20D does not perform de-emphasis on the signals SIGA to SIGC as shown in FIG. 24B. As a result, the differences AB, BC, CA have the waveforms shown in FIG. 25B.

  When the symbol transits from "+ x" to "-y", the signal generator 11D sets the signals EA, EB, and EC to "0", "1", and "0", as shown in FIG. To do. As a result, the transmission unit 20D performs de-emphasis on the signal SIGB, as shown in FIG. 24C, and makes a transition from the low-level voltage VL to a voltage higher than the low-level voltage VL. At this time, the transmission unit 20D does not perform deemphasis on the signals SIGA and SIGC. As a result, the differences AB, BC, CA have the waveforms shown in FIG. 25C. That is, in this example, the difference CA that transits over “0” is not affected by the de-emphasis.

  When the symbol transits from "+ x" to "+ z", the signal generator 11D sets the signals EA, EB, EC to "0", "0", "0" as shown in FIG. . As a result, the transmission unit 20D does not perform de-emphasis on the signals SIGA to SIGC as illustrated in FIG. 24D. As a result, the differences AB, BC, CA have the waveforms shown in FIG. 25D.

  When the symbol transits from "+ x" to "-z", the signal generator 11D sets the signals EA, EB, and EC to "1", "0", and "0", as shown in FIG. To do. As a result, the transmission unit 20D performs de-emphasis on the signal SIGA and transitions from the high level voltage VH to a voltage lower than the high level voltage VH, as shown in FIG. 24E. At this time, the transmission unit 20D does not perform de-emphasis on the signals SIGA and SIGB. As a result, the differences AB, BC, CA have the waveforms shown in FIG. 25E. That is, in this example, the difference BC that transits over “0” is not affected by the de-emphasis.

  In this way, the transmitter 10D performs de-emphasis so as not to affect one of the differences AB, BC, and CA that crosses over "0". Even with this configuration, the same effect as that of the communication system 1 according to the above-described embodiment can be obtained.

  Note that, among the transitions among the six symbols, the transition for which de-emphasis is performed is not limited to the example in FIG. 23, and it is possible to arbitrarily set which transition to perform de-emphasis.

[Modification 1-5]
In the above-described embodiment, the signal generator 11 uses the LUT 19 stored in the register 12 to generate the signals EA, EB, and EC. At this time, the LUT 19 may be configured so that the pre-emphasis setting can be changed. The communication system 1E according to this modification will be described below in detail.

  FIG. 26 illustrates a configuration example of the communication system 1E. The communication system 1E includes a receiving device 30E and a transmitting device 10E. The communication system 1E changes the pre-emphasis setting based on the result of transmitting and receiving a predetermined pattern for calibration.

  FIG. 27 illustrates a configuration example of the receiving device 30E. The reception device 30E has a signal generation unit 36E. The signal generator 36E has a pattern detector 37E. In the calibration mode, the pattern detection unit 37E compares the pattern of the signal received by the reception device 30E with a predetermined pattern for calibration, and supplies the comparison result to the transmission device 10E as a signal DET.

  FIG. 28 illustrates a configuration example of the transmission device 10E. The transmission device 10E has a LUT generation unit 16E. The LUT generation unit 16E generates the LUT 19 based on the signal DET and stores it in the register 12.

  In the communication system 1E, the pre-emphasis setting is changed in the calibration mode so that the bit error rate becomes low, for example. Specifically, first, the transmission device 10E transmits signals SIGA to SIGC having a predetermined pattern for calibration. Then, the receiving device 30E receives the signals SIGA to SIGC, the pattern detection unit 37E compares the pattern of the received signal with a predetermined pattern for calibration, and notifies the transmitting device 10E of the comparison result. To do. Then, the LUT generation unit 16E of the transmission device 10E changes the pre-emphasis setting based on the comparison result. In the communication system 1E, by such an operation, the setting of pre-emphasis is changed so that the bit error rate becomes low, for example. Then, after the pre-emphasis setting is completed, the calibration mode is terminated and normal data transmission is performed. Such calibration may be performed, for example, when the power is turned on, periodically, or when the amount of data to be exchanged is small.

[Modification 1-6]
In the above embodiment, the LUT 19 indicating the relationship between the current symbol CS, the signals TxF, TxR, TxP, and the signals EA, EB, EC is used, but the present invention is not limited to this, and instead of this, For example, the LUT indicating the relationship between the next symbol NS, the signals TxF, TxR, TxP, and the signals EA, EB, EC may be used, or, for example, the current symbol CS and the next symbol NS may be used. May be used as the LUT indicating the relationship between the signals EA, EB, and EC.

[Modification 1-7]
In the above-described embodiment, as shown in FIG. 13 and the like, pre-emphasis is performed during the period of transmitting one symbol, but the present invention is not limited to this, and instead of this, for example, FIG. , 30, pre-emphasis may be performed only for a predetermined period after the transition of the signals SIGA, SIGB, SIGC. 29 and 30 show the case where the symbol transits from "+ x" to "+ y". As shown in FIG. 29, the transmission unit 20 performs pre-emphasis only for a predetermined period after the transition of the signals SIGA, SIGB, SIGC. At this time, the difference AB becomes like the waveform W21 of FIG. 30, and the difference BC becomes like the waveform W23 of FIG. If pre-emphasis is not performed on the signals SIGA to SIGC, for example, the difference AB has a waveform W22 in FIG. 30 and the difference BC has a waveform W24 in FIG. That is, in such a case, since the transition of the waveform is dull, the eye may be narrowed. On the other hand, in this modification, since the pre-emphasis is performed only for a predetermined period after the transition of the signals SIGA, SIGB, SIGC, the eye can be widened and the communication quality can be improved.

[Other modifications]
Also, two or more of these modified examples may be combined.

<2. Second Embodiment>
Next, the communication system 2 according to the second embodiment will be described. The communication system 2 is intended to improve communication quality by using an equalizer. That is, in the communication system 1 according to the first embodiment described above, the transmission device 10 performs pre-emphasis on the signals SIGA to SIGC, but in this communication system 2, the reception device changes the signals to SIGA to SIGC. On the other hand, the equalization is performed. That is, the same components as those of the communication system 1 according to the first embodiment described above are designated by the same reference numerals, and the description thereof will be appropriately omitted.

  As shown in FIG. 1, the communication system 2 includes a transmitter 40 and a receiver 60. In the communication system 2, the transmitter 40 does not perform pre-emphasis on the signals SIGA to SIGC, and the receiver 60 equalizes the signals SIGA to SIGC.

  FIG. 31 illustrates a configuration example of the transmission device 40. The transmission device 40 includes a signal generation unit 41 and a transmission unit 50. The signal generation unit 41, like the signal generation unit 11 according to the first embodiment, obtains the next symbol NS based on the current symbol CS, the signals TxF, TxR, TxP, and the clock TxCK, and outputs the signal S1. Is output as. That is, the signal generation unit 41 omits the function of generating the signals EA, EB, and EC from the signal generation unit 11. The transmission unit 50 generates signals SIGA, SIGB, and SIGC based on the signal S2.

  FIG. 32 illustrates a configuration example of the transmission unit 50. The transmission unit 50 has an output control unit 21 and output units 22A, 22B, 22C. That is, the transmission unit 50 is obtained by omitting the emphasis control unit 23 and the output units 24A to 24C from the transmission unit 20 according to the first embodiment.

  FIG. 33 illustrates a configuration example of the receiving device 60. The receiving device 60 includes an equalizer 61, receiving units 62 and 63, first-in first-out (FIFO) memories 66 and 67, and a selector 68.

  The equalizer 61 increases the high frequency component of the signal SIGA and outputs it as the signal SIGA2, increases the high frequency component of the signal SIGB and outputs it as the signal SIGB2, and increases the high frequency component of the signal SIGC and outputs it as the signal SIGC2. is there.

  The reception unit 62 generates signals RxF1, RxR1, RxP1 and a clock RxCK1 based on the equalized signals SIGA2, SIGB2, SIGC2. The receiver 62 includes amplifiers 32A, 32B and 32C, a clock generator 33, flip-flops 34 and 35, and a signal generator 36. That is, the receiving unit 62 has the same configuration as the receiving device 30 according to the first embodiment.

  The receiving unit 63 generates signals RxF2, RxR2, RxP2 and a clock RxCK2 based on the unequalized signals SIGA, SIGB, SIGC. The receiving unit 63 includes amplifiers 32A, 32B and 32C, a clock generating unit 33, flip-flops 34 and 35, a signal generating unit 65, and a register 64. That is, the receiving unit 63 replaces the signal generating unit 36 with the signal generating unit 65 in the receiving unit 62 and adds the register 64.

  Similar to the signal generation unit 36, the signal generation unit 65 generates signals RxF2, RxR2, RxP2 based on the output signals of the flip-flops 34, 35 and the clock RxCK2. Further, the signal generation unit 65 also has a function of generating the signal SEL based on the LUT 59 supplied from the register 64. The signal SEL is one of the signals RxF1, RxR1, RxP1 generated based on the equalized signals SIGA2, SIGB2, SIGC2 and the signals RxF2, RxR2, RxP2 generated based on the non-equalized signals SIGA, SIGB, SIGC. It shows which is selected. The LUT 59 shows, for example, the relationship among the current symbol CS2, the signals RxF2, RxR2, RxP2, and the signal SEL, and is similar to the LUT 19 or the like according to the first embodiment, for example. The signal generator 65 is adapted to generate and output the signal SEL by referring to the LUT 59 based on the current symbol CS2 and the signals RxF2, RxR2 and RxP2.

  The register 64 stores the LUT 59. The LUT 59 is written in the register 64 by an application processor (not shown) when the receiving device 60 is powered on, for example.

  The FIFO memory 66 is a buffer memory that temporarily stores the signals RxF1, RxR1, and RxP1 supplied from the receiving unit 62. In this example, the FIFO memory 66 is adapted to write and read data using the clock RxCK1.

  The FIFO memory 67 is a buffer memory that temporarily stores the signals RxF2, RxR2, RxP2 and the signal SEL supplied from the receiving unit 63. In this example, the FIFO memory 67 is configured to write data by using the clock RxCK2 and read data by using the clock RxCK1.

  The selector 68 selects the signals RxF1, RxR1, RxP1 read from the FIFO memory 66 or the signals RxF2, RxR2, RxP2 read from the FIFO memory 67 based on the signal SEL read from the FIFO memory 67, The signals are output as signals RxF, RxR, and RxP.

  Here, the transmission device 40 corresponds to a specific but not limitative example of “transmission device” in one embodiment of the present disclosure. The receiving device 60 corresponds to a specific but not limitative example of “receiving device” in one embodiment of the present disclosure. The signals SIGA, SIGB, and SIGC correspond to a specific example of “one or more transmission signals” in the present disclosure. The reception unit 63 corresponds to a specific but not limitative example of “first reception unit” in one embodiment of the present disclosure. The signals RxF2, RxR2, RxP2 correspond to a specific but not limitative example of “first output signal” in one embodiment of the present disclosure. The equalizer 61 corresponds to a specific but not limitative example of “equalizer” in one embodiment of the present disclosure. The reception unit 62 corresponds to a specific but not limitative example of “second reception unit” in one embodiment of the present disclosure. The signals RxF1, RxR1, RxP1 correspond to a specific but not limitative example of “second output signal” in one embodiment of the present disclosure. The register 64 and the signal generation unit 65 correspond to a specific but not limitative example of “selection control unit” in one embodiment of the present disclosure.

  Next, some of the symbol transitions will be described in detail as an example.

  34 and 35 show the operation when the symbol transits from "+ x" to "+ y". FIGS. 34A to 34C show the waveforms of the equalized signals SIGA2, SIGB2 and SIGC2. 35A to 35C respectively show waveforms of a difference AB2 between the signals SIGA2 and SIGB2, a difference BC2 between the signals SIGB2 and SIGC2, and a difference CA2 between the signals SIGC2 and SIGA2. In this example, the lengths of the transmission lines 9A to 9C are sufficiently short.

  When the symbol transits from "+ x" to "+ y", the equalizer 61 generates the signals SIGA2 to SIGC2 by emphasizing the transition in the signals SIGA to SIGC, as shown in FIG. At this time, the differences AB2, BC2, CA2 are as shown in FIG. Thus, in the communication system 2, the eye can be widened by performing equalization and making the waveform transition steep. Therefore, in such a transition, the selector 68 selects the signals RxF1, RxR1, and RxP1 generated based on the equalized signals SIGA2, SIGB2, and SIGC2, and outputs them as the signals RxF, RxR, and RxP.

  36 and 37 show the operation when the symbol transits from "+ x" to "-z", and FIGS. 36A to 36C show the waveforms of the equalized signals SIGA2, SIGB2 and SIGC2. 37A to 37C respectively show the waveforms of the differences AB2, BC2, CA2.

  Even when the symbol transits from "+ x" to "-z", the equalizer 61 emphasizes the transition in the signals SIGA to SIGC to generate the signals SIGA2 to SIGC2, as shown in FIG. At this time, the differences AB2, BC2, CA2 are as shown in FIG. As described above, in the waveform of the difference AB2, as shown in FIG. 37 (A), an undershoot may occur during the transition, and the eye may be narrowed. Therefore, in such a transition, the selector 68 selects the signals RxF2, RxR2, RxP2 generated based on the non-equalized signals SIGA, SIGB, SIGC, and outputs them as the signals RxF, RxR, RxP.

  As described above, in the communication system 2, since the signals SIGA, SIGB, and SIGC are selectively equalized, for example, when the transition is such that the eye becomes narrower when the equalization is performed, the equalization is performed. You can avoid it. Thereby, the communication quality can be improved in the communication system 2.

  As described above, in the present embodiment, since the signals SIGA to SIGC are selectively equalized, the communication quality can be improved.

[Modification 2-1]
In the above-described embodiment, the signal generation unit 65 of the reception unit 63 is configured to generate the signal SEL, but the present invention is not limited to this, and instead of this, for example, the signal generation unit 36 of the reception unit 62 is The signal SEL may be generated. Further, the signal generation unit 36 of the reception unit 62 and the signal generation unit 65 of the reception unit 63 may generate the signals SEL, and the selector 68 may perform the selection operation based on these signals SEL.

[Modification 2-2]
Further, the communication system may be configured by combining the transmitting device 10 according to the first embodiment and the receiving device 60 according to the present embodiment. In this case, the transmission device 10 performs pre-emphasis on the signals SIGA, SIGB, SIGC, and the reception device 60 performs equalization on the signals SIGA, SIGB, SIGC, and thus the longer transmission lines 9A, 9B, 9C. It is possible to send and receive data via.

<3. Application example>
Next, an application example of the communication system described in the above embodiment and modification will be described.

  FIG. 38 shows an appearance of a smartphone 300 (multifunctional mobile phone) to which the communication system according to any of the above-described embodiments and the like is applied. Various devices are mounted on the smartphone 300, and the communication system such as the above-described embodiment is applied to a communication system for exchanging data between these devices.

  FIG. 39 illustrates a configuration example of the application processor 310 used in the smartphone 300. The application processor 310 includes a CPU (Central Processing Unit) 311, a memory control unit 312, a power supply control unit 313, an external interface 314, a GPU (Graphics Processing Unit) 315, a media processing unit 316, and a display control unit 317. And a MIPI (Mobile Industry Processor Interface) interface 318. In this example, the CPU 311, the memory control unit 312, the power supply control unit 313, the external interface 314, the GPU 315, the media processing unit 316, and the display control unit 317 are connected to the system bus 319, and mutually exchange data via the system bus 319. You can interact with each other.

  The CPU 311 processes various information handled by the smartphone 300 according to the program. The memory control unit 312 controls the memory 501 used when the CPU 311 performs information processing. The power supply control unit 313 controls the power supply of the smartphone 300.

  The external interface 314 is an interface for communicating with an external device, and is connected to the wireless communication unit 502 and the image sensor 503 in this example. The wireless communication unit 502 wirelessly communicates with a base station of a mobile phone, and includes, for example, a baseband unit, an RF (Radio Frequency) front end unit, and the like. The image sensor 503 acquires an image, and is configured to include a CMOS sensor, for example.

  The GPU 315 performs image processing. The media processing unit 316 processes information such as voice, characters, and figures. The display control unit 317 controls the display 504 via the MIPI interface 318. The MIPI interface 318 sends an image signal to the display 504. As the image signal, for example, a signal of YUV format or RGB format can be used. As the communication system between the MIPI interface 318 and the display 504, for example, the communication system according to the above-described embodiment or the like is applied.

FIG. 40 shows a configuration example of the image sensor 410. The image sensor 410 includes a sensor unit 411, an ISP (Image Signal Processor) 412, a JPEG (Joint Photographic Experts Group) encoder 413, a CPU 414, a RAM (Random Access Memory) 415, and a ROM (Read Only Memory) 416. , A power control unit 417, an I ² C (Inter-Integrated Circuit) interface 418, and a MIPI interface 419. In this example, each of these blocks is connected to a system bus 420, and data can be exchanged with each other via the system bus 420.

The sensor unit 411 acquires an image and is composed of, for example, a CMOS sensor. The ISP 412 performs a predetermined process on the image acquired by the sensor unit 411. The JPEG encoder 413 encodes the image processed by the ISP 412 to generate an image in the JPEG format. The CPU 414 controls each block of the image sensor 410 according to a program. The RAM 415 is a memory used when the CPU 414 performs information processing. The ROM 416 stores a program executed by the CPU 414. The power supply controller 417 controls the power supply of the image sensor 410. The I ² C interface 418 receives control signals from the application processor 310. Although not shown, the image sensor 410 receives a clock signal in addition to the control signal from the application processor 310. Specifically, the image sensor 410 is configured to operate based on clock signals of various frequencies. The MIPI interface 419 is for transmitting an image signal to the application processor 310. As the image signal, for example, a signal of YUV format or RGB format can be used. As the communication system between the MIPI interface 419 and the application processor 310, for example, the communication system according to the above-described embodiment or the like is applied.

  Although the present technology has been described above with reference to some embodiments and modifications, and application examples to electronic devices, the present technology is not limited to these embodiments and the like, and various modifications are possible. is there.

  For example, in each of the above embodiments, the signals SIGA, SIGB, and SIGC are assumed to transit between the three voltage states SH, SM, and SL, but the present invention is not limited to this, and instead of this, Thus, for example, it may transition between two voltage states, or it may transition between four or more voltage states.

  Further, for example, in each of the above-described embodiments, communication is performed using three signals SIGA, SIGB, and SIGC, but the present invention is not limited to this, and instead of this, for example, two signals are used. The communication may be performed, or the communication may be performed using four or more signals.

  It should be noted that the effects described in the present specification are merely examples and are not limited, and may have other effects.

  1, 1E, 2 ... Communication system, 9A-9C ... Transmission line, 1010B, 10E, 40 ... Transmitting device, 11, 11B ... Signal generating section, 12 ... Register, 13-15, 14B, 15B ... Flip-flop, 16E ... LUT generation section, 19, 19B, 59 ... LUT, 20, 20B, 50 ... Transmission section, 21 ... Output control section, 22A-22C ... Output section, 23 ... Emphasis control section, 24A-24C ... Output section, 25 , 26 ... Transistor, 27, 28 ... Resistor element, 30, 30E, 60 ... Receiving device, 31A to 31C ... Resistor element, 32A to 32C ... Amplifier, 33 ... Clock generating unit, 34, 35 ... Flip-flop, 36, 36E ... signal generator, 37E ... pattern detector, 61 ... equalizer, 62, 63 ... receiver, 64 ... register, 65 ... signal generator, 66, 67 ... FIFO Memory, 68 ... Selector, 100, 110 ... Symbol determination section, 120, 130, 140, 150, 160, 170 ... Logical circuit, 121-125 ... Logical product circuit, 180 ... Logical sum circuit, AB, BC, CA, AB2 , BC2, CA2 ... Difference, CS, CS2, NS, PS2 ... Symbol, EA-EC, EE, EA2-EC2, EE2, SEL, SIGA-SIGC, SIGA2-SIGC2, S1, S2, RxF, RxR, RxP, RxF1. , RxR1, RxP1, RxF2, RxR2, RxP2, TxF, TxR, TxP ... Signal, DET ... Signal, EM ... Eye mask, SH, SL, SM ... Voltage state, RxCK, RxCK1, RxCK2, TxCK ... Clock, TinA, TinB , TinC ... Input terminal, TJ ... Jitter, ToutA, ToutB, ToutC ... Output terminal, VH High-level voltage, VL ... low-level voltage, VM ... mid-level voltage, V1 ... voltage.

Claims (17)

A first receiving unit that receives one or more transmission signals and outputs a first output signal;
An equalizer for equalizing the one or more transmission signals;
A second receiving unit that receives the one or more transmission signals equalized by the equalizer and outputs a second output signal,
The equalizer is a receiving device that selectively equalizes the one or more transmission signals based on a transition pattern of the one or more transmission signals. Each of the one or more transmission signals has a first voltage state, a second voltage state, and a voltage level between the voltage level of the first voltage state and the voltage level of the second voltage state. The receiving device according to claim 1, wherein the receiving device makes a transition to and from a third voltage state having a. A selection control unit that selects one of the first output signal and the second output signal based on the transition pattern of the one or more transmission signals,
The selection control unit obtains a sequence of voltage states in the one or more transmission signals, compares two voltage states temporally adjacent to each other, and based on the comparison result, the first output signal or the first output signal. The receiving device according to claim 1, wherein the output signal of 2 is selected. A selection control unit that selects one of the first output signal and the second output signal based on the transition pattern of the one or more transmission signals,
The selection control unit includes a look-up table indicating a relationship between the transition pattern and a flag indicating whether or not to perform equalization, and based on the look-up table, the first output signal or the second output signal. The receiving device according to claim 1 or 2, wherein the output signal is selected. The receiving device according to claim 4, wherein the look-up table is configured to be programmable. The receiving device according to claim 1, wherein the equalizer performs equalization so as to increase a high frequency component of the one or more transmission signals. A transmitter for transmitting one or more transmission signals;
A receiving device for receiving the one or more transmission signals,
The receiving device,
A first receiving unit that receives the one or more transmission signals and outputs a first output signal;
An equalizer for equalizing the one or more transmission signals;
A second receiver that receives the one or more transmission signals equalized by the equalizer and outputs a second output signal;
A selection control unit that selects one of the first output signal and the second output signal based on a transition pattern of the one or more transmission signals. Each of the one or more transmission signals has a first voltage state, a second voltage state, and a voltage level between the voltage level of the first voltage state and the voltage level of the second voltage state. The communication system according to claim 7, wherein the communication system transits to and from a third voltage state having a. The selection control unit obtains a sequence of voltage states in the one or more transmission signals, compares two voltage states temporally adjacent to each other, and based on the comparison result, the first output signal or the first output signal. 9. The communication system according to claim 7, wherein the output signal of 2 is selected. The selection control unit includes a look-up table indicating a relationship between the transition pattern and a flag indicating whether or not to perform equalization, and based on the look-up table, the first output signal or the second output signal. 9. The communication system according to claim 7, wherein the output signal is selected. The communication system according to claim 10, wherein the look-up table is configured to be programmable. The communication system according to any one of claims 7 to 11, wherein the equalizer performs equalization so as to increase a high frequency component of the one or more transmission signals. The communication system according to any one of claims 7 to 12, wherein the equalizer selectively equalizes the one or more transmission signals based on the transition pattern of the one or more transmission signals. The transmitter is
A transmitter that generates the one or more transmission signals by selectively performing emphasis based on a data signal;
The transmission control part which judges whether emphasis is performed based on the transition pattern of the said data signal, and controls the said transmission part, The communication system as described in any one of Claim 7 to 13. The communication system according to claim 14, wherein the transmission unit selectively performs emphasis so as to selectively increase a high frequency component of the one or more transmission signals. The communication system according to claim 14, wherein the transmission section selectively performs emphasis so as to selectively reduce low-frequency components of the one or more transmission signals. Further comprising an imaging device that acquires an image by performing an imaging operation,
The communication system according to any one of claims 7 to 14, wherein the transmission device transmits the image as the one or a plurality of transmission signals.

Images