JPH0113472Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a bidirectional signal transmission circuit used, for example, in a handshake circuit reset signal generation circuit between a main circuit and a slave circuit in a digital circuit.

[Prior art]

A conventional circuit of this type is shown in FIG. In the figure, 1 is a main circuit that controls the entire device, 2 is a slave circuit that controls input/output devices, etc. based on commands from the main circuit 1, and 3 is a data exchange between the main circuit 1 and the slave circuit 2. A data line that transfers
4 is a latch circuit that temporarily stores that data from main circuit 1 to slave circuit 2 is prepared; 5 is main circuit 1;
6 is a hardware reset line by which the main circuit 1 resets the slave circuit 2 in terms of hardware, and 7 is an OR circuit.

Next, the operation will be explained. Data generated in the main circuit 1 is passed to the slave circuit 2 through the data line 3. At this time, the main circuit 1 outputs a strobe signal to the latch circuit 4 after the data to the data line 3 is correctly set. When the latch circuit 4 receives this strobe signal from the main circuit 1, it sets its output to logic "1" and notifies the slave circuit 2 that the data to the data line 3 is correctly set. The main circuit 1 is notified that the slave circuit 2 has not yet taken in the data on the data line 3. Slave circuit 2 receiving signal from latch circuit 4
After reading the state of the data line 3, it outputs a handshake reset signal to the OR circuit 7 to notify that data has been taken in normally. When the OR circuit 7 receives the handshake reset signal from the slave circuit 2, it outputs a logic "1" to the latch circuit 4, which resets the latch circuit 4 to its original state and outputs a logic "0". . Recognizing that the output of the latch circuit 4 is logic "0", the main circuit 1 determines that the slave circuit 2 has normally received the data on the data line 3, and a series of data transfers ends. In addition, independent of these data transfers, there is a hardware reset line 6 from the main circuit 1 to the slave circuit 2, and by driving this signal line from the main circuit 1, the slave circuit 2 and the latch circuit 4 are reset. I do.

Since data transfer in the conventional main circuit and slave circuit is configured as described above, it is necessary to provide separate reset lines for the handshake circuit and hardware reset line, especially when connecting the main circuit with a cable. When a slave circuit is connected, there are many types of signal lines, which has the disadvantage of causing problems in operation.

[Summary of the idea]

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and by transmitting two types of signals with different purposes and transmission directions through one bidirectional signal line, it is possible to change the type of signal line. The purpose of the present invention is to provide a bidirectional signal transmission circuit that can reduce the

[Example of idea]

An embodiment of this invention will be described below with reference to the drawings. In Fig. 2, 1 is a main circuit that controls the entire device, 2 is a slave circuit that controls input/output devices, etc. based on the commands of this main circuit 1, and 3 is a main circuit 1 of these main circuits.
A data line 4 transfers data between the main circuit 1 and the slave circuit 2, a latch circuit 4 temporarily stores that data is prepared from the main circuit 1 to the slave circuit 2, and a latch circuit 8 transfers data from the main circuit 1 to the slave circuit 2. 2 is a driver circuit for a handshake reset signal that notifies that it has been received; 9 is a driver circuit for a hardware reset signal that causes the main circuit 1 to reset the slave circuit 2 in terms of hardware; 10 is a driver circuit for driver circuits 8 and 9; Bidirectional reset signal line with wired OR connected to
Reference numeral 11 denotes an integrating circuit that extracts only the hardware reset signal from the bidirectional reset signal line 10 to the slave circuit 2.

Further, an example of the configuration of the integrating circuit 11 is shown in FIG. In FIG. 3, 11a and 11c are inverters having hysteresis characteristics for inverting and outputting the input signal level, and 11b is an integrating circuit composed of a resistor and a capacitor.

Next, the operation will be explained. The data generated in the main circuit 1 is passed to the slave circuit 2 through the data line 2, and the latch circuit 4 notifies the main circuit 1 and the slave circuit 2 of the data transfer status, which is the same as in the conventional system. It is. At this time, the slave circuit 2, which has finished acquiring data in response to the notification from the latch circuit 4, outputs a handshake reset signal to the driver circuit 8. The driver circuit 8 thereby drives the bidirectional reset signal line 10 from the slave circuit side. This operation resets the latch circuit 4 to its original state, and notifies the main circuit 9 that the data acquisition of the slave circuit 2 has been completed normally. In addition to these data transfers, the main circuit 1 can output a hardware reset signal to the slave circuit 2 through the bidirectional reset signal line 10 by driving the driver circuit 9. The bidirectional reset signal line 10 thus passes two types of signals with different purposes and transmission directions, but the signals are separated by the integrating circuit 11, which detects only the hardware reset signal and sends it to the slave circuit 2. Reset. For this operation, the handshake reset signal output from the slave circuit 2 uses a narrow pulse, and the hardware reset signal output from the main circuit 1 uses a wide pulse.

The operation of the integrating circuit 11 will be explained based on an example of its configuration. In FIG. 3, inverter 11a is connected to bidirectional reset signal line 10. In FIG.

When a narrow pulse is input to the inverter 11a, its output is output as a narrow pulse whose level is inverted. When a narrow pulse with this width is input to the integrating circuit 11b, the output level of the integrating circuit 11b hardly changes due to its characteristics. Therefore, the output of the inverter 11c does not change in any way from before the narrow pulse was input. On the other hand, when a wide pulse is input to the inverter 11a, its output becomes a wide pulse whose level is inverted. When this wide pulse is input to the integrating circuit 11b, its output changes greatly. This change is detected by the inverter 11c, which outputs a wider pulse due to the hysteresis characteristic. In this way, by using an integrating circuit, it is possible to selectively operate on pulses having different time widths. This situation is shown in FIG.

[Effect of idea]

As described above, this invention enables control with fewer signal lines by using a signal selection circuit using bidirectional signal lines and an integrating circuit, making it easier and cheaper to configure a signal transmission circuit using a cable connection. There is an effect that can be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional handshake reset circuit, FIG. 2 is a block diagram of a bidirectional reset signal circuit according to an embodiment of the present invention, and FIG. 3 is an example of the configuration of the integrating circuit in FIG. Figure 4 is the third
FIG. 3 is an operation diagram of the integrating circuit shown in FIG. 1... Main circuit, 2... Slave circuit, 3... Data line, 4... Latch circuit, 5... Handshake reset line, 6... Hardware reset line, 7...
...OR circuit, 8...Driver circuit, 9...Driver circuit, 10...Bidirectional reset line, 11...
In the integrating circuit, the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] one bidirectional signal line, a driver circuit connected to both ends of the bidirectional signal line and transmitting and outputting transmission control signals having different pulse widths in opposite directions, and one end side of the bidirectional signal line. a two-way signal transmission circuit, which is connected to an integrating circuit that integrates both transmission control signals with a predetermined time constant and outputs a control signal from the other end in a direction opposite to the transmission direction of the driver circuit on the one end. .