JPH0512055A - Microprocessor unit selection control circuit - Google Patents

Abstract

PURPOSE:To permit the only MPU requiring internal diagnosis to perform an internal diagnostic operation by reducing the circuit while making computer communication interface one, eliminating the replacement of cables, and transmitting an internal diagnostic command with the use of a control line different from a serial data signal line. CONSTITUTION:When a data bus selection signal is outputted from an internal diagnostic device 4, a data bus selection circuit 8 performs the connection between a MPU1A and an SIO2 and outputs the internal diagnostic command from the internal diagnostic device 4 as usual. The command of the serial data is converted into parallel data by the SIO2, and the SIO2 outputs an RxRDY signal to an interrupt signal generation circuit 7. An interrupt signal 11 outputted by the interrupt signal generation circuit 7 and the outputted data bus selection signal are entered into the interrupt signal selection circuit 9, and the interrupt signal selection circuit 9 outputs an interrupt signal only to the MPU1A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microprocessor unit selection control circuit by a computer communication line, and more particularly to an internal diagnostic control of a circuit using two microprocessor units.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a conventional example.
2 shows a microprocessor unit (hereinafter referred to as MPU) selection control circuit using a computer communication line such as an RS-232C line. As shown in FIG. 2, RS-232C interfaces are provided for the two MPUs 1A and 1B, respectively, and when trying to diagnose the state of each MPU 1A, 1B with one internal diagnostic device 4, use an RS-232C cable. I was going while changing them.
Alternatively, an internal diagnostic device is prepared for each MPU 1A, 1B for diagnosis.

[0003]

In this conventional internal diagnostic method, since the MPU desired to be internally diagnosed cannot be selected from the internal diagnostic device, the RS-232C cable provided in the MPU desired to be internally diagnosed may be replaced. It was either necessary or required two internal diagnostic devices. One serial input / output chip (hereinafter referred to as SIO) for each MPU.
However, there is a problem that the circuit itself becomes large.

[0004]

A microprocessor unit selection control circuit according to the present invention is designed so that a computer communication interface is first provided to reduce the size of the circuit and a computer communication cable is provided. I lost the replacement. Then, one control line is provided separately from the serial data line, and a data bus selection signal is placed on this control line and is input to the data bus selection circuit. The data bus can be connected between. In addition, since only the MPU performing data communication is to perform interrupt processing, by inputting both the interrupt signal and the data bus selection signal to the interrupt signal selection circuit, only the MPU performing data communication will receive the interrupt signal. Is input.

The present invention is directed to a plurality of microprocessor
Between the microprocessor unit and the serial input / output chip for data communication according to a data bus select signal externally input via a computer communication line to enable data communication with one of the units. A data bus selection circuit for connecting a data bus, and the microprocessor for performing data communication.
Only the unit is provided with an interrupt signal selection circuit for inputting the interrupt signal and the data bus selection signal.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the MPU selection circuit of the present invention, which uses RS-232 as a computer communication line.
An example using the C line is shown.

In FIG. 1, when the two MPUs 1A and 1B are accessing the RAMs 3A and 3B, respectively, an internal diagnostic device 4 connected to the RS-232C line is used.
The operation when the internal diagnosis of the MPU 1A is performed will be described. First, when performing internal diagnosis, MPU1
In order to enable the data communication between A and SIO2, the internal diagnostic device 4 outputs the data bus selection signal on the data bus selection signal line 10 of the control line provided separately from the serial data 6. When this data bus selection signal is input to the data bus selection circuit 8, the data bus selection circuit 8 connects the data bus 5 between the MPU 1A and SIO2. As a result, the data communication between the MPU 1A and SIO 2 becomes possible. After that, the internal diagnostic device 4 outputs the internal diagnostic command to the serial data line 6 as usual. The command sent as serial data is S
Converted to parallel data by IO2, SIO2 outputs the RxRDY signal to the interrupt signal generation circuit 7, and the interrupt signal generation circuit 7 outputs the interrupt signal 11. The interrupt signal 11 and the previously output data bus selection signal are input to the interrupt signal selection circuit 9. The interrupt signal selection circuit 9 is MP
The interrupt signal is output only to U1A. This allows the MPU
It is possible to have only 1A perform an interrupt process. Through the above process, the MPU 1A can be selected from the internal diagnostic device 4 and data communication can be performed. A similar process is possible when selecting the MPU 1B.

[0008]

As described above, according to the present invention, one computer communication interface is used to reduce the size of the circuit, and one computer communication cable is used to eliminate replacement of the cable. In addition, a control line is provided separately from the serial data signal line, a data bus selection signal is output to this control line, and then an internal diagnostic command is sent as usual, so that internal diagnostic operation is performed only on the MPU for which internal diagnosis is desired. It has an effect that can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an MPU selection control circuit of the present invention.

FIG. 2 is a block diagram showing a conventional example.

[Explanation of symbols]

 1A, 1B MPU 2 SIO 3A, 3B RAM 4 Internal diagnostic device 5 Data bus 6 Serial data line 7, 7A, 7B Interrupt signal generation circuit 8 Data bus selection circuit 9 Interrupt signal selection circuit 10 Data bus selection signal line 11, 11A, 11B interrupt signal line

Claims (1)

Claim: What is claimed is: 1. A microprocessor for performing data communication according to a data bus selection signal input from the outside via a computer communication line to enable data communication with one of a plurality of microprocessor units. A data bus selection circuit for connecting a data bus between the processor unit and the serial input / output chip,
A microprocessor unit selection control circuit, comprising: an interrupt signal selection circuit that inputs an interrupt signal and the data bus selection signal only to the microprocessor unit that performs data communication.