JPH03209581A - Microprocessor - Google Patents

Abstract

PURPOSE:To enable a processing by a new control program only by connecting a ROM storing the new control program to the external part of a microprocessor by providing a circuit to execute the read and decision of a certain external determined address and to generate a control signal at initial time before executing the processing. CONSTITUTION:At the initial time, an external ROM recognition and control signal generation part 5 reads the external specified address, decides the data and controls a built-in ROM gate 2 and an external ROM gate 6. Therefore, the microprocessor itself recognizes whether the ROM is connected in the external part or not, and the reading destination of the control program can be switched to either a built-in ROM or an external ROM. Thus, when the ROM is not connected in the external part, the processing is executed by the control program stored in the built-in ROM, and when the ROM is connected in the external part, the processing can be executed by the control program stored in the external ROM.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a microprocessor incorporating a ROM containing a control program.

BACKGROUND OF THE INVENTION When troubleshooting a malfunction in a microprocessor that has a built-in ROM containing a conventional control program or checking the operation of a newly developed control program, it is necessary to use the ROM. Either a new manufacturing process for writing data had to be started, or an evaluation type of microprocessor had to be developed.

Problems to be Solved by the Invention However, since the semiconductor manufacturing process takes a long time, prompt troubleshooting is not possible, and
When developing an evaluation type, there were drawbacks such as high development costs.

In order to solve the above problems, the present invention recognizes whether the microprocessor itself is connected to an external ROM,
The purpose is to execute a new control program by simply connecting a ROM containing a new control program to the outside of the microprocessor.

Means for Solving the Problems In order to achieve this object, the microprocessor of the present invention reads a specific external address at the initial time before processing, judges the read data, and has a circuit that generates a control signal. The device has a configuration in which the control signal can be used to switch the readout destination of the control program to either the built-in ROM or the external ROM.

Effect By having the above configuration, the present invention has an external ROM.
The microprocessor itself recognizes whether or not the ROM is connected, and the control program can be read from the built-in ROM or external ROM.
If M is not connected, the process can be executed by the control program stored in the built-in ROM, and if the ROM is connected externally, the process can be executed by the control program stored in the external ROM. .

Embodiment FIG. 1 is a block diagram showing an embodiment of a microprocessor according to the present invention. In FIG. 1, reference numeral 1 denotes a built-in ROM containing a control program, which is connected to a data bus 3 via a built-in ROM gate 2, and is also connected to an address bus 4. Reference numeral 5 denotes an external ROM recognition and control signal generation section, which is connected to the data bus 3 and address bus 4 and sends control signals 7 and 8 to the built-in ROM gate 2 and the external ROM gate 6. Reference numeral 9 denotes a control section, an arithmetic section, and other circuit blocks, which are connected to the data bus 3 and address bus 4. 10 is an external ROM. Figure 2 shows the external R.
This is a simplified diagram of OMl0 and an external ROM recognition and control signal generation section.

The external ROM recognition and control signal generating section 5 is connected to the external ROM 10 via an address bus 4 and a data bus 3, and the data bus 12 is pulled up. or,(
a) is a diagram when there is an external ROM, and (bl is a diagram when there is no external ROM).

At the initial time before processing, the external ROM recognition and control signal generating section 5 shuts off the built-in ROM gate 2 and turns on the external ROM gate 6.

Next, the external ROM recognition and control signal generation section 5 outputs a specific address A to access the outside. At this time, if an external ROM is connected, by putting 0 in the address A of the external ROM 10 as shown in FIG. Therefore, assuming that the ROM10 is connected to the outside, the built-in ROM gate 2 is shut off, the external ROM gate 6 is made conductive, and the process is then executed using the control program stored in the external ROM10. When the external ROM is not connected, when address A is accessed, the data read by pulling up the data bus is 1, so the external ROM recognition and control signal generation section 5 is connected to the external ROM. recognize that it is not
The built-in ROM gate 2 is made conductive, the external ROM gate 6 is cut off, and then processing is executed by the control program stored in the built-in ROM.

As described above, according to this embodiment, the external ROM recognition and control signal generation section 5 reads out a specific external address at the initial time, determines the data, and
By controlling the external ROM gate 6, the microprocessor itself recognizes whether or not an external ROM is connected, and selects the internal ROM from which to read the control program.
It is possible to switch between M and external ROM.

It goes without saying that in FIG. 2, the data stored in address A of the external ROM 10 may be set to 1 and the data bus may be pulled down.

Effects of the Invention As described above, according to the present invention, by having a circuit that reads and determines a certain external address at the initial time before executing a process and generates a control signal, the microprocessor itself can connect to an external ROM. It is possible to recognize whether the R
By simply connecting the OM to the outside of the microprocessor, a new control program can execute the process.

[Brief explanation of drawings]

Figure 1 is a block diagram of a microprocessor in one embodiment of the present invention, and Figures 2 (a) and (b) are externally connected RO
1 when M is connected and when it is not connected...
・・Built-in ROM, 2・・・Built-in ROM gate, 3
...Data bus, 4 ...Address bus, 5
...External ROM recognition and control signal generation section, 6.
---External ROM gate, 7...Built-in RO
M gate control signal, 8...external ROM gate control signal, 9...control unit. Arithmetic unit, other circuit blocks, 10...External OMo

Claims (1)

[Claims] It has a ROM (read-only memory) that contains a control program, and a circuit that reads a specific external address at the initial time before processing, determines the contents of the read data, and generates a control signal. The microprocessor itself determines whether ROM is connected or not,
If no external ROM is connected, the control program stored in the built-in ROM executes the process, and the external ROM is connected.
A microprocessor characterized in that when a microprocessor is connected, processing is executed by a control program stored in an external ROM.