JP2001160816A - Usb controller, printer and usb control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a USB controller where no glitch is superimposed on a data wire in a USB cable. SOLUTION: The USB controller 1 is provided with a transceiver 4, a control IC 5, and a CPU 6. The USB controller 1 transmits/receives data to/from a host computer 2 via a USB cable 3. The transceiver generates differential signals D+, D- supplied to a data line in the USB cable based on a differential 1 control signal and a single end 0 control signal supplied from the control IC. The control IC 5 prevents a logic of the differential 1 control signal and a logic of the single end 0 control signal from being simultaneously changed. Thus, no undesired glitch is caused in the differential signals D+, D-.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a USB (Universal)
USB for data transmission using Serial Bus) cable
Related to a control device.

[0002]

2. Description of the Related Art As a standard of a standard interface for connecting a computer and peripheral devices, USB (Universal)
al Serial Bus). The USB can connect up to 127 peripheral devices, and can perform data transmission with each peripheral device at a maximum transmission speed of 12 Mbit / sec. In addition, USB supports hot plug that allows connection / disconnection while power is supplied to computers and peripheral devices, and is standard as an interface for many peripheral devices such as keyboards, mice, modems, printers, and scanners. It is expected to be used.

[0003] As shown in FIG.
Two data lines consisting of twisted pairs and power supply lines Vcc and Vdd
And four lines. Differential signals having different logics are transmitted to the data lines.

[0004] In the USB, the level of one data line signal D + is higher than the level of the other data line signal D- "differential 1" level, and the level of the data line signal D + is higher than the level of the data line signal D-. Is smaller than the “differential 0” level and the levels of data line signals D + and D− are both 0.
Communication is performed using three levels, that is, a “single-end 0” level smaller than 8V.

FIG. 6 is a block diagram showing a schematic configuration of a conventional USB control device.
2 shows a configuration of a B control device. The USB control device 1 shown in FIG.
The data is transmitted and received via. The USB control device 1 shown in FIG. 6 includes a transceiver 4 for converting a signal level and a control IC 5 for transmitting and receiving data to and from the transceiver 4.
And a CPU 6.

[0006] Inside the transceiver 4, a transmission buffer and a reception buffer are provided. The transmission buffer converts the data from the control IC 5 into a differential signal D conforming to the USB standard.
The data is converted into + and D- and supplied to the data line. The reception buffer converts the differential signals D + and D− transmitted from the host computer 2 via the USB cable 3 into logic level data and supplies the data to the control IC 5.

There are several modes for transmitting data via the USB cable 3. Hereinafter, representative first mode and second mode will be described.

[0008] The first mode is characterized in that the D + control signal and the D- control signal are individually controlled.
FIG. 8 is a diagram showing a signal waveform in the first mode.
As shown in the figure, when the phases of the D + control signal and the D- control signal are inverted, the differential signal D + has the same logic as the D + control signal, and the differential signal D- has the same logic as the D- control signal. Be logical. On the other hand, when both the D + control signal and the D- control signal are at a low level, both the differential signals D + and D- are at a low level.

[0009]

However, the propagation delay times of the D + control signal and the D- control signal are not always the same, and as shown in FIG. Is generated. Due to this difference in the delay time, the cross voltage of the differential signals D + and D− deviates from the center value of the signal amplitude.

On the other hand, the second mode is characterized in that there is no problem as in the first mode. In the second mode, differential signals D + and D- are generated by transmitting a single-ended 0 control signal and a differential 1 control signal from the control IC 5 to the transceiver 4.

FIG. 8 shows a signal waveform in the second mode. As shown in the figure, while the single-end 0 control signal is at a low level, the transceiver 4 outputs a differential signal D +, based on the differential 1 control signal supplied from the control IC 5.
Generate D-. Specifically, the logic of signal D + is changed to differential 1
The control signal is made almost the same, and the logic of the signal D- is inverted from that of the differential 1 control signal. On the other hand, when the single-end 0 control signal goes high, both differential signals D + and D- go low.

As described above, in the second mode, while the single-end 0 control signal is at the low level, the differential signal D
+ And D- depend only on the logic of the differential 1 control signal. Therefore, the crossing voltage of the differential signals D + and D− becomes a substantially intermediate voltage of the signal amplitude, and the signal quality can be guaranteed.

However, as shown at time T6 in the figure, the time when the single-end 0 control signal changes and the time when the differential
When the time when the control signal changes is close, the signal D
When-starts to rise, the single-ended 0 control signal becomes high level, so that an undesired glitch is generated in the signal D-, and the signal quality is degraded.

SUMMARY OF THE INVENTION The present invention has been made in view of such a point, and an object of the present invention is to provide a USB control device in which a glitch is not superimposed on a data line in a USB cable.

[0015]

Means for Solving the Problems In order to solve the above problems, the invention of claim 1 is based on a USB (Universal Serial Serial).
Bus) A transceiver for transmitting and receiving data to and from two data lines in a cable, and a control for supplying first and second control signals corresponding to the data supplied to the two data lines to the transceiver. And a circuit, wherein when the first control signal has a first logic, a logic of the two data lines is changed according to a logic of the second control signal;
In the case where the first control signal has the second logic, in a USB control device for fixing the logic of the two data lines, the control circuit may control the signal level of the first control signal to There is provided timing control means for controlling the supply timing of the first and second control signals to the transceiver so that the signal level of the second control signal does not change substantially simultaneously.

According to the present invention, the timing of the first and second control signals is controlled so that the signal levels of the first and second control signals do not change substantially simultaneously.

According to the second aspect of the present invention, when the EOP is transmitted to two data lines in the USB cable, glitches are prevented from occurring by performing timing control of the first and second control signals. .

According to the third aspect of the present invention, the timing of the first and second control signals is adjusted so that the glitch is not superimposed on the data line in the USB cable in the process of generating the EOP.

According to the fourth aspect of the present invention, when USB transmission is performed between the printer and the host computer, glitch is not generated, so that print quality can be improved.

The invention according to claim 5 is based on a USB (Universal Servo).
ial bus) is a USB control method for supplying a transceiver with first and second control signals corresponding to data supplied to two data lines in a cable, wherein the first control signal is a first logic signal. In the case of, the logic of the two data lines is changed according to the logic of the second control signal, and
When the first control signal has the second logic, in a USB control method for fixing the logic of the two data lines, the signal level of the first control signal and the signal level of the second control signal are fixed. The supply timing of the first and second control signals to the transceiver is controlled so that the signal levels do not change substantially simultaneously.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a USB control device, a printer and a USB control method according to the present invention will be specifically described with reference to the drawings. Hereinafter, the USB control device built in the printer will be mainly described.

The present embodiment is characterized in that no glitch is generated in the differential signals D + and D- transmitted through the USB cable 3.

The USB control device 1 according to the present invention includes a transceiver 4, a control IC 5, and a CPU 6, as in FIG. The USB control device 1 includes a host computer 2
, Data is transmitted and received via the USB cable 3. The data sent from the host computer 2 to the USB control device 1 is, for example, print data, and the data sent from the USB control device to the host computer 2 is, for example, printer status information.

When USB transmission is performed in the above-described second mode, the control IC 5 supplies a differential 1 control signal and a single-ended 0 control signal to the transceiver 4. Based on these control signals, the transceiver 4
It generates differential signals D + and D- to be supplied to two data lines in the cable 3.

An example in which data is transmitted and received in the above-described second mode will be described below.

FIG. 1 is a flowchart showing the processing operation of the control IC 5, FIG. 2 is a timing chart of the USB control device according to the present invention, and FIG. 3 is a diagram showing the internal configuration of the transceiver 4 in the USB control device 1.

As shown in FIG. 3, the transceiver 4 includes AND gates G1 and G2 for performing a predetermined logical operation based on the differential 1 control signal and the single-ended 0 control signal, and inverters IV1 and IV2 (the logical operation circuit 11). ) And AN
A transmission buffer 1 that converts the outputs of the D gates G1 and G2 to a USB voltage level and supplies the USB voltage to the USB cable 3
2a and 12b and reception buffers 13a and 13b for converting data transmitted from the USB cable 3 to a logic level.

The control IC 5 controls the transceiver 4
A differential 1 control signal and a single-ended 0 control signal are provided. When the single-ended 0 control signal is at a high level,
The outputs of the AND gates G1 and G2 in the transceiver 4 are always at a low level. When the single-ended 0 control signal is at a low level, the AND gate G1 outputs a signal having the same logic as the differential 1 control signal, and the AND gate G2 outputs an inverted signal of the differential 1 control signal.

FIG. 4 is a diagram showing the structure of data transmitted via the USB cable 3. USB as shown
According to the standard, data is transmitted in units of a packet composed of a plurality of bits (for example, 8 bits, 16 bits, 32 bits, and 64 bits). Each packet includes an SOP (Start Of Packet) indicating the head of the packet, a data body,
It consists of EOP (End Of Packet) indicating the end of the packet.

The EOP is composed of a two-bit time single-ended 0 followed by a one-bit time differential 1. Here, the single end 0 is a USB cable 3
Both the signals D + and D− in the middle are lower than 0.8 V, and the differential 1 indicates that the signal level of the signal D + is higher than the signal level of the signal D−.

Hereinafter, based on the flowchart of FIG.
The operation of the control IC 5 will be described. First, the control IC 5
It is determined whether it is necessary to transmit data to the host computer via the SB cable (step S
1).

If it is not necessary to transmit data, the process remains at step S1. If it is necessary to transmit data, a differential 1 control signal and a single-ended 0 control signal for the second mode transmission are generated. (Step S2). At this time, as described later, the logic of the differential 1 control signal and the logic of the single-ended 0 control signal are not changed at the same time. Next, the generated differential 1 control signal and single-ended 0 control signal are transmitted to the transceiver (Step S).
3).

FIG. 2 is a timing waveform diagram of the differential 1 control signal, the single-ended 0 control signal, and the data line output from the control IC 5, and the data body of the packet is transmitted from time T1 to time T5. The following shows an example of transmitting an EOP.

Conventionally, when the EOP is transmitted, as shown in FIG. 8, the logic of the differential 1 control signal and the logic of the single-ended 0 control signal may change almost simultaneously.
In the case of the present embodiment, the logic of the differential 1 control signal and the logic of the single-ended 0 control signal are not changed at the same time. Specifically, as shown at time T6 in FIG. 2, when the logic of the differential 1 control signal is changed while the single-ended 0 control signal is at the high level, and then the single-ended 0 control signal is changed to the low level. (Time T7 in FIG. 2)
Fixes the logic of the differential 1 control signal. As a result, no glitch occurs in the signals D + and D-.

As described above, the control circuit of this embodiment does not change the logic of the differential 1 control signal and the logic of the single-ended 0 control signal at the same time, so that the differential signals D + and D When generating-, an unwanted glitch as shown at time T6 in FIG. 8 does not occur. Therefore, the signal quality of USB transmission is improved, and a malfunction of the device on the receiving side is less likely to occur.

In the above-described embodiment, the USB control device built in the printer has been described as an example. However, the present invention can be applied to various electronic devices having a USB interface other than the printer.

[0037]

As described above in detail, according to the present invention, the signal level of the first control signal and the signal level of the second control signal are prevented from simultaneously changing during USB transmission. Therefore, glitches (hazards) do not occur on the data lines in the USB cable. Therefore, signal quality is improved, and malfunction during USB transmission can be prevented.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a processing operation of a control IC 5.

FIG. 2 is a timing chart of the USB control device according to the present invention.

FIG. 3 is a diagram showing an internal configuration of a transceiver 4 in the USB control device 1.

FIG. 4 is a view showing the structure of data transmitted via a USB cable 3.

FIG. 5 is a view showing the structure of a USB cable.

FIG. 6 is a block diagram showing a schematic configuration of a conventional USB control device.

FIG. 7 is a diagram showing a signal waveform in a first mode.

FIG. 8 is a diagram showing a signal waveform in a second mode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 USB control device 2 Host computer 3 USB cable 4 Transceiver 5 Control IC 6 CPU 11 Logical operation circuit 12-14 Flip-flop 15a, 15b Transmission buffer 16a, 16b Receiving buffer

Claims (5)

[Claims] 1. A transceiver for transmitting and receiving data to and from two data lines in a USB (Universal Serial Bus) cable, and a first transceiver corresponding to data supplied to the two data lines.
And a control circuit for supplying a second control signal to the transceiver. When the first control signal has a first logic, the second control signal is supplied to the transceiver.
The logic of the two data lines is changed in accordance with the logic of the control signal, and when the first control signal is the second logic, the logic of the two data lines is fixed. USB
In the control device, the control circuit may be configured to transmit the first and second control signals to the transceiver so that a signal level of the first control signal and a signal level of the second control signal do not change substantially simultaneously. A USB control device comprising timing control means for controlling supply timing of the USB. 2. Data is transmitted to the two data lines in units of a packet composed of a plurality of bits, and an EOP (End Of End) indicating the end of the packet is provided at the end position of each packet.
And the timing control means changes the signal level of the first control signal and the signal level of the second control signal substantially simultaneously when transmitting the EOP to the two data lines. The USB control device according to claim 1, wherein a supply timing of the first and second control signals to the transceiver is controlled so as not to be performed. 3. The EOP according to claim 1, wherein, after a first state in which both of the two data lines are both set to a low level continues for a plurality of bits, one of the two data lines is set to a high level and another one of the two data lines is set to a low level. At least one second state that causes the book to go low
The timing control means controls the first and second control signals so that the signal levels of the first and second control signals do not simultaneously change when switching from the first state to the second state.
3. The USB control device according to claim 2, wherein a timing of supplying the second control signal to the transceiver is controlled. 4. A printer incorporating the USB control device according to claim 1. 5. A USB control method for supplying, to a transceiver, first and second control signals corresponding to data supplied to two data lines in a USB (Universal Serial Bus) cable, Is the first logic, the second control signal
The logic of the two data lines is changed in accordance with the logic of the control signal, and when the first control signal is the second logic, the logic of the two data lines is fixed. USB
In the control method, the first control signal and the second control signal are controlled so that a signal level of the first control signal and a signal level of the second control signal do not change substantially simultaneously.
And controlling the supply timing of the second control signal to the transceiver.