JP2002016487A - Two-way transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously transmit signals between both the sides without increasing the number of signal lines. SOLUTION: In one two-way transmitter 20a, a signal to be transmitted to a transmitting party is converted into a voltage signal corresponding to the level of that signal and sent the signal through a signal line 31 by a driver 21a. In this case, the direction of a current flowing through the signal line 31 is detected by first current detecting circuits 22a and 22b and the level of the transmitting party is decided by a decision circuit 24a on the basis of the current direction and the level of that signal transmitted to the transmitting party. In another bidirectional transmitter 20b, similar decision is performed as well. Thus, when exchanging signals between devices, for example, the signals can be simultaneously transmitted between both the devices even without increasing the number of signal lines.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bidirectional transmission device used, for example, for transmitting signals bidirectionally between devices or for transmitting signals bidirectionally between circuits in an LSI.

[0002]

2. Description of the Related Art In conventional digital signal transmission, a signal to be transmitted to a transmission partner is converted into a voltage signal corresponding to its level (1 or 0 if binary) and applied to a signal line. This is performed by detecting a voltage signal. This method has been widely used in electronic circuits using digital signals since ancient times, and is also widely used in digital devices such as personal computers at present.

[0003] By the way, such a transmission system requires at least one signal line, and two signal lines are required to transmit signals bidirectionally between the two.
That is, for example, in the transmission of a signal that requires 128 signal lines in one direction, in order to realize this in two directions, one signal is required.
28 × 2 = 256 signal lines are required. As described above, in order to transmit a signal in both directions, double signal lines in one direction are required. For example, in the case of a circuit having many signal lines such as a CPU bus, the number of signal lines is reduced. However, there is a disadvantage that the wiring area increases.

Here, the above-mentioned conventional transmission system will be described with reference to FIGS. FIG. 5 is a diagram showing a configuration of a bidirectional bus according to a conventional transmission system, and FIG. 6 is an operation transition diagram showing an operation state of the bidirectional bus of FIG.

Now, assume that a binary signal is bidirectionally transmitted between the device 1 and the device 2. As shown in FIG. 5, eight signals indicated by AI0 to AI7 are converted into voltage signals by a voltage driving circuit (driver) 3a provided on the device 1 side and output to each signal line (on a bus). . These signals are taken in by the input circuit 4b of the device 2 via each signal line, and transmitted to the next circuit as AO0 to AO7. In this case, as shown in FIG. 6, when the signals of AI0 to AI7 on the device 1 side are at the L level, the signals of AO0 to AO7 on the device 2 side are also at the L level. When the signals of AI0 to AI7 on the device 1 side are at the H level, AO0 to AO
The signal of No. 7 also becomes H level.

In the case of bi-directional transmission, another circuit (voltage drive circuit 3b and input circuit 4b) similar to the above is prepared and a signal is transmitted. That is, eight signal lines are provided from the device 2 to the device 1, and the device 2
To BI7 are converted into voltage signals by a voltage drive circuit 3b provided on the device 2 side and output to each signal line (on the bus). These signals are captured by the input circuit 4a of the device 1 and transmitted to the next circuit as BO0 to BO7. In this case, as shown in FIG. 6, when the signals of BI0 to BI7 on the device 2 side are at L level,
The signals of BO0 to BO7 on the device 1 side are also at the L level. When the signals BI0 to BI7 on the device 2 side are at the H level, the signals BO0 to BO7 on the device 1 are also at the H level.

As described above, when the conventional transmission system is used to perform bidirectional transmission, the number of signal lines increases, and the wiring area increases accordingly.

As a means for solving such a drawback, there is a method of performing bidirectional transmission using one signal line in a time division manner.

FIG. 7 shows a transmission method based on the time division.
This will be described with reference to FIG. FIG. 7 is a configuration diagram of a conventional bidirectional bus using a time-division transmission method, and FIG. 8 is an operation transition diagram showing an operation state of the bidirectional bus of FIG.

When signals are transmitted bidirectionally between device 1 and device 2, voltage drive circuits (drivers) 5a and 5b with output control and input circuits 4a and 4b are provided in device 1 and device 2, respectively. . Assuming that voltage drive circuits 5a and 5b are active low, control signal O
When EA (OEB) is at L level, AI0 to AI7
A signal indicated by (BI0 to BI7) is output to each signal line (on the bus). When the control signal OEA (OEB) is at the H level, the output of the voltage drive circuit 5a (5b) is in a high impedance (non-drive) state, thereby preventing signal collision.

Here, when a signal is transmitted from the device 1 to the device 2 (AI → AO), OEA = L level and OEB = H level. Thereby, the device 2
The output of the voltage drive circuit 5b on the side becomes a high impedance (non-drive) state, and the signals indicated by AI0 to AI7 are output via the respective signal lines. These signals are
The input signal 4b is taken in and transmitted as AO0 to AO7 to the next circuit. In this case, as shown in FIG. 8, when the signals of AI0 to AI7 on the device 1 side are at the L level, the signals of AO0 to AO7 on the device 2 side are also at the L level. When the signals of AI0 to AI7 on the device 1 side are at the H level, AO0 to AO
The signal of No. 7 also becomes H level.

On the other hand, when a signal is transmitted from the device 2 to the device 1 (BI → BO), OEA = H level,
OEB = L level. This time, the output of the voltage drive circuit 5a on the device 1 side becomes a high impedance (no drive) state, and signals indicated by BI0 to BI7 are output via the respective signal lines. These signals are captured by the input circuit 4a of the device 1 and transmitted to the next circuit as BO0 to BO7. In this case, as shown in FIG. 8, when the signals of BI0 to BI7 on the device 2 side are at L level,
The signals of BO0 to BO7 on the device 1 side are also at the L level. When the signals BI0 to BI7 on the device 2 side are at the H level, the signals BO0 to BO7 on the device 1 are also at the H level.

As described above, according to the time-division transmission method, signals can be transmitted bidirectionally by using a common signal line between the device 1 and the device 2. However, in this method, since the signal lines are used in a time-division manner, signals cannot be transmitted between the two at the same time, resulting in a disadvantage that the transmission speed is reduced.

[0014]

As described above, the conventional transmission system has a problem that the number of signal lines increases and the wiring area increases accordingly. Further, in order to solve such a problem, when a signal line is used in a time-division manner and transmitted in both directions, a signal cannot be transmitted between the two at the same time, and the transmission speed decreases accordingly. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide a bidirectional transmission apparatus capable of transmitting signals between both at the same time without increasing the number of signal lines. I do.

[0016]

SUMMARY OF THE INVENTION The present invention is a bidirectional transmission device for transmitting a binary signal bidirectionally to a transmission partner via a common signal line, and transmitting the binary signal to the transmission partner. Driver means for converting a signal to be transmitted into a voltage signal corresponding to the level of the signal and transmitting the signal to the signal line, and current detection for detecting a direction of a current flowing through the signal line when the signal is transmitted by the driver means Means for determining the level of the signal transmitted by the transmission partner via the signal line at the same time based on the direction of the current detected by the current detection means and the level of the own signal transmitted to the transmission partner. And determination means for performing the determination.

According to such a configuration, the level of the signal of the other party can be determined from the direction of the current flowing through the signal line and the level of the own signal. Therefore, for example, in a case where signals are exchanged between devices, signals can be transmitted between them at the same time without increasing the number of signal lines.

If the direction of the current flowing through the signal line and the current value at that time are detected, it is possible to determine a multi-level signal.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration between devices having the bidirectional transmission device of the present invention.

Now, it is assumed that a signal is bidirectionally transmitted between the device 10a and the device 10b. The device 10a and the device 10b are provided with bidirectional transmission devices 20a and 20b, respectively, and these bidirectional transmission devices 20a and 20b exchange signals bidirectionally via the bidirectional bus 30.

FIG. 2 shows a specific configuration.

The bidirectional transmission device 20a provided on the device 10a side includes a driver 21a and the driver 21a.
, A first current detection circuit 22a, a second current detection circuit 23a, and a determination circuit 24a. These circuits are provided for each signal line constituting the bidirectional bus 30.

The driver 21a communicates with a transmission partner (device 1).
0b) is a voltage drive circuit that converts a signal to be transmitted to 0b) into a voltage signal corresponding to the level of the signal and sends out the signal to the signal line 31. Here, since the transmission of the binary signal is assumed, the voltage level is switched between when the signal is at the H level and when the signal is at the L level.

The first current detection circuit 22a and the second current detection circuit 23a detect the direction of the current flowing through the signal line 31. Among these, the first current detection circuit 22a detects a current flowing from the device 10a to the device 10b (A → B direction), and the second current detection circuit 23a
The current flowing from b to the device 10a (B → A direction) is detected. The dotted line in the figure indicates the direction in which the current flows.

The determination circuit 24a is provided with the first current detection circuit 2
2a, the output signal of the second current detection circuit 23a, and the signal transmitted by the device 10a to the device 10b are input and transmitted to the direction of the current flowing through the signal line 31 and the transmission partner (device 10b). The level of the signal transmitted by the transmission partner via the signal line 31 at the same time is determined based on the level of the own signal.

The bidirectional transmission device 20b provided on the device 10b side has the same configuration. That is, the bidirectional transmission device 20b provided on the device 10b side
A driver 21b, a first current detection circuit 22b, a second current detection circuit 23b connected to the driver 21b,
It is composed of a judgment circuit 24b. These circuits are provided for each signal line constituting the bidirectional bus 30.

The driver 21b communicates with the transmission partner (device 1
0a) is a voltage driving circuit that converts a signal to be transmitted to a voltage signal corresponding to the level of the signal and sends out the voltage signal to the signal line 31. . Here, since it is assumed that a binary signal is transmitted,
The voltage level is switched between when the signal is at the H level and when the signal is at the L level.

The first current detection circuit 22b and the second current detection circuit 23b detect the direction of the current flowing through the signal line 31. The first current detection circuit 22b detects the current flowing from the device 10b to the device 10a (in the direction from B to A), and the second current detection circuit 23b detects the current flowing from the device 10b.
The current flowing from a to the device 10b (A → B direction) is detected. The dotted line in the figure indicates the direction in which the current flows.

The determination circuit 24b includes the first current detection circuit 2
2b, the output signal of the second current detection circuit 23b, and the signal transmitted by the device 10b to the device 10a are input and transmitted to the direction of the current flowing through the signal line 31 and the transmission partner (device 10a). The level of the signal transmitted by the transmission partner via the signal line 31 at the same time is determined based on the level of the own signal.

Next, the bidirectional transmission device 20a,
20b, points A to B in FIG. 2 (device 10a
To device 10b), from point B to point A (device 10b
The principle of operation when signals are simultaneously transmitted from the device to the device 10a) will be described.

Assuming that an H-level signal is transmitted from point A to point B and an H-level signal is transmitted from point B to point A, the driver 21a on the device 10a side and the driver 21b on the device 10b side transmit the H-level signal, respectively. To output
Both have the same potential, and no current flows through the signal line 31.

Here, from the point A side, that is, from the device 10a side, that no current flows through the signal line 31 means that
It can be determined that the transmission partner (device 10b) is transmitting the same H-level signal as itself. The same applies to the point B side, that is, the device 10b side.
When a current does not flow through the signal line 31 when an H-level signal is transmitted from the
It can be determined that the a) side also emits the same H level signal as itself.

From point A to point B, an L level signal, B
Even when an L-level signal is transmitted from point A to point A, the two have the same potential, and no current flows through the signal line 31.
Therefore, from the point A side, that is, from the device 10a side, the fact that no current flows through the signal line 31 can be determined to mean that the transmission partner (device 10b) side is outputting the same L level signal as itself. This is the same on the point B side, that is, on the device 10b side. When no current flows through the signal line 31 when the L level signal is transmitted from the device 10b, the transmission partner (device 10a) side also becomes itself. It can be determined that the same L level signal is output.

Next, assuming that an L-level signal is transmitted from point A to point B and an H-level signal is transmitted from point B to point A, a current flows in the direction from driver 21b to driver 21a on signal line 31. (B → A direction). Therefore, if this current direction is detected by the current detection circuits (22a, 23a, 22b, 23b) provided at the respective points, the level of the signal of the transmission partner can be easily obtained by comparing the current direction with the level of its own output signal. It is possible to estimate.

In this case, on the point A side, that is, on the device 10a side, a current in the B → A direction is detected by the second current detection circuit 23a. Since the direction of the current flowing through the signal line 31 is in the direction of B → A and the signal transmitted from the device 10a is at L level, the determination circuit 24a has transmitted the H level signal from the transmission partner (device 10b). Is determined. On the other hand, on the point B side, that is, on the device 10b side, the current in the B → A direction is detected by the first current detection circuit 22b. Since the direction of the current flowing through the signal line 31 is in the B → A direction and the signal transmitted from the device 10b is at the H level, the determination circuit 24b transmits the L level signal from the transmission partner (device 10a). Is determined.

From the point A to the point B, an H level signal, B
Assuming that an L-level signal is transmitted from the point to the point A, a current flows on the signal line 31 from the driver 21a to the driver 21b (A → B direction). Therefore, in the same manner as described above, it is possible to easily estimate the level of the signal of the transmission partner based on the current direction at that time and its own signal level.

In this case, the current in the direction A → B is detected by the first current detection circuit 22a on the point A side, that is, on the device 10a side. Since the direction of the current flowing through the signal line 31 is in the A → B direction and the signal transmitted from the device 10a is at the H level, the determination circuit 24a transmits the L level signal at the transmission partner (device 10b) side. Is determined. On the other hand, on the point B side, that is, on the device 10b side, the current in the A → B direction is detected by the second current detection circuit 23b. Since the direction of the current flowing through the signal line 31 is from A to B and the signal transmitted from the device 10b is at L level, the determination circuit 24b has transmitted the H level signal from the transmission partner (device 10a). Is determined.

FIG. 3 shows an operation transition diagram of a bidirectional bus using the bidirectional transmission device of FIG.

In FIG. 3, the value at point A is the device 1
0a, that is, the level of the signal transmitted from the driver 21a to the signal line 31. What is the value of point B?
The level of the output signal of the device 10b, that is, the level of the signal transmitted from the driver 21b to the signal line 31 is shown.

The value at point A2 is the second value on the device 10a side.
The level of the output signal of the current detection circuit 23a is H level when a current in the B → A direction is flowing through the signal line 31, and is L level when no current is flowing through the signal line 31. The value of the point A3 is the first value on the device 10a side.
The level of the output signal of the current detection circuit 22a is H level when a current in the A → B direction is flowing through the signal line 31, and is L level when no current is flowing through the signal line 31.

The value at the point B2 is the second value on the device 10b side.
The level of the output signal of the current detection circuit 23b is H level when a current in the A → B direction is flowing through the signal line 31, and is L level when no current is flowing through the signal line 31. The value of the point B3 is the first value on the device 10b side.
The level of the output signal of the current detection circuit 22b is H level when a current in the B → A direction is flowing through the signal line 31, and is L level when no current is flowing through the signal line 31.

The output A is the result of the judgment by the judgment circuit 24a provided on the device 10a side, and indicates the signal level of the other side, that is, the signal level of the device 10b. The B output is a determination result of the determination circuit 24b provided on the device 10b side, and indicates the signal level of the partner, that is, the signal of the device 10a.

As described above, when the device 10a and the device 10b are transmitting signals of the same level at the same time, no current flows through the signal line 31. Therefore, it can be determined that the own signal level is the level of the signal of the other party. For example, when the device 10a transmits an L-level signal and does not flow through the signal line 31, it is determined that the device 10b of the transmission partner is also transmitting the L-level signal.

When the devices 10a and 10b are transmitting signals of different levels at the same time, a current flows through the signal line 31. In this case, as shown in FIG.
When b is at the L level, a current in the A → B direction flows. Conversely, when the device 10a is at the L level and the device 10b is at the H level, a current flows in the B → A direction. Therefore, the level of the signal transmitted by the other party at the same time can be determined from the current direction at that time and the own signal level. For example, when the device 10a transmits an H level signal, the signal line 31
By detecting that the current in the direction A → B flows through the device 10b, it is determined that the device 10b of the transmission partner is transmitting the L-level signal. Similarly, when the device 10a transmits an L-level signal, the signal line 31 has B → A
By detecting that a current in the direction is flowing, it is determined that the transmission partner device 10b is transmitting an H-level signal.

As described above, since the level of the signal of the transmission partner can be determined from the direction of the current flowing through the signal line 31 (including the case where the current does not flow) and the level of its own signal,
By using the signal line 31 commonly for the device 10a and the device 10b, it is possible to transmit signals of both directions at the same time in both directions.

In the above embodiment, transmission of a binary signal (H level signal and L level signal) has been described. However, even in the case of transmitting a multi-level signal, the current detection circuit (22
a, 23a, 22b, 23b), if a function capable of detecting the current value at that time is added in addition to the current direction, bidirectional transmission of a multilevel signal is possible based on the same principle as described above.

The following description is made on the assumption that a signal having three levels of -1, 0 and +1 is transmitted.

FIG. 4 shows an operation transition diagram when a ternary signal is transmitted. Here, in order to make the description easy to understand, the values of the points A2, A3, B2, and B3 in FIG. 4, that is, the current detection circuits (22a, 23a, 22b, and 23b)
Is represented by a current value such as 2I, I, 0.
The current value 2I indicates that the current value is twice as large as the current value I as a reference value, and the current value 0 indicates that no current flows. Actually, for example, the current value 2I is set to +1 level,
The current value I is replaced with a signal of level 0, and the current value 0 is replaced with a signal of level −1, and the current detection circuits (22a, 23a, 22b, 2)
3b) to the determination circuit (24a, 24b).

Here, the device 10a and the device 10b
Are transmitting the same level of signal at the same time, no current flows through the signal line 31. Therefore, it can be determined that the level of the own signal is the level of the signal of the other party.
For example, when the device 10a transmits a -1 level signal and does not flow through the signal line 31, it can be determined that the device 10b of the transmission partner is also transmitting a -1 level signal. Similarly, when the device 10a transmits the signal of the 0 level and the signal is not flowing through the signal line 31, it can be determined that the device 10b of the transmission partner is also transmitting the signal of the 0 level. If the signal is not flowing through the signal line 31 when the signal is transmitted, it can be determined that the device 10b of the transmission partner is also transmitting the signal of the +1 level.

When the device 10a is transmitting a signal having a higher potential level than the device 10b, a current in the direction A → B flows through the signal line 31. At this time, the device 10a determines that the signal at the point A2 is at the 0 level, the value at the point A3 is at the I level, and that the signal of the other party is at the -1 level when its own signal is at the 0 level. Further, the value of the point A2 is 0 level, the value of the point A3 is 2I level, and the own signal is +
It is determined that the signal of the other party is at -1 level when the level is 1 level, the value at point A2 is 0 level, the value at point A3 is I level,
When the own signal is at the +1 level, it is determined that the signal of the other party is at the 0 level. A similar determination can be made on the device 10b side.

On the other hand, when the device 10a is transmitting a signal having a lower potential level than the device 10b, a current in the B → A direction flows through the signal line 31. At this time, the device 10a determines that the signal of the other party is at the 0 level when the value of the point A2 is at the I level, the value of the point A3 is at the 0 level, and the own signal is at the -1 level. Further, the value of the point A2 is at the 2I level, the value of the point A3 is at the 0 level, and the own signal is −
It is determined that the signal of the other party is at +1 level when it is at 1 level, the value at point A2 is at I level, the value at point A3 is at 0 level,
When the own signal is at the 0 level, it is determined that the signal of the other party is at the +1 level. A similar determination can be made on the device 10b side.

As described above, when a signal having two or more values is transmitted, it is possible to determine the signal of the transmission partner by detecting the signal including the current value at that time. Therefore, the device 10a and the device 1
It is possible to use the signal line 31 in common with Ob to transmit the signals in both directions at the same time.

In the above embodiment, the case where signals are bidirectional between devices has been described as an example. However, the present invention is not limited to this. For example, signals are transmitted bidirectionally in a circuit such as an LSI. Even if it does, it can be applied.

[0055]

As described above in detail, according to the bidirectional transmission apparatus of the present invention, in the case of exchanging signals between devices, for example, signals are transmitted between both at the same time without increasing the number of signal lines. Can be transmitted. Therefore, the number of signal lines can be reduced and the circuit scale (wiring scale) can be reduced as compared with the case where bidirectional transmission is realized by two signal lines as in the related art. Further, since the signal lines are not used in a time-division manner and the signal lines can be used between them at the same time, high-speed transmission can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration between devices provided with a bidirectional transmission device of the present invention.

FIG. 2 is a diagram showing a configuration of a bidirectional bus according to the present invention.

FIG. 3 is an operation transition diagram showing an operation state of the bidirectional bus in FIG. 2;

FIG. 4 is an operation transition diagram when a ternary signal is transmitted.

FIG. 5 is a diagram showing a configuration of a bidirectional bus according to a conventional transmission method.

FIG. 6 is an operation transition diagram showing an operation state of the bidirectional bus in FIG. 5;

FIG. 7 is a configuration diagram of a conventional bidirectional bus using a time-division transmission method.

FIG. 8 is an operation transition diagram showing an operation state of the bidirectional bus in FIG. 7;

[Explanation of symbols]

 10a, 10b device 20a, 20b bidirectional transmission device 30 bidirectional bus 31 signal line 21a, 21b driver 22a, 22b first current detection circuit 23a, 23b second current detection circuit 24a, 24b ... Judgment circuits 1, 2... Devices 3a, 3b... Voltage drive circuits (drivers) 4a, 4b... Input circuits 5a, 5b.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J056 AA01 AA04 BB53 DD29 EE11 GG05 5K018 AA02 BA01 CA03 CA05 EA10 JA03 5K029 AA18 CC01 DD04 FF03 GG07 HH08 JJ06 KK24

Claims (2)

[Claims] 1. A bidirectional transmission device for bidirectionally transmitting a binary signal to a transmission partner via a common signal line, wherein a signal to be transmitted to the transmission partner is set to the signal level. A driver for converting the signal into a corresponding voltage signal and sending the signal to the signal line; a current detecting means for detecting a direction of a current flowing through the signal line when the signal is sent by the driver; Based on the direction of the detected current and the level of its own signal transmitted to the transmission partner,
A bidirectional transmission device comprising: a determination unit configured to determine a level of a signal transmitted by a transmission partner via the signal line at the same time. 2. A bi-directional transmission device for bi-directionally transmitting a multi-level signal to a transmission partner via a common signal line, wherein a signal to be transmitted to the transmission partner is set to the level of the signal. A driver means for converting the voltage into a corresponding voltage signal and sending the signal to the signal line; a current detecting means for detecting a direction and a current value of a current flowing through the signal line when the signal is sent by the driver means; Based on the direction and current value of the current detected by the current detecting means and the level of its own signal transmitted to the transmission partner, the level of the signal transmitted by the transmission partner via the signal line at the same time is determined. A bidirectional transmission device comprising: a determination unit.