JPH05342094A - Computer device - Google Patents

Abstract

PURPOSE:To reload an application program onto a system while eliminating necessity for providing a ROM exclusive for IPL program storage even when any abnormality such as the destruction of the IPL program is generated at the computer device to be operated while writing the application program in the electrically erasable ROM. CONSTITUTION:A program storage address on an IPL memory card is set samely as the reset start address. Therefore, when the IPL memory card is connected, an application ROM chip select signal is suppressed by an IPLON signal supplied through a connector and after a hardware is reset, the IPL program is automatically read from the IPL memory card and executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a computer device which operates in a form in which an application program is written in an electrically erasable ROM provided inside a device.

[0002]

2. Description of the Related Art For a device which operates by writing an application program in an electrically erasable ROM provided inside the device, as shown in FIG. 4, a control program for changing a program (hereinafter referred to as an IPL program) Using a dedicated ROM for storing
As shown in FIG. 2, there is one in which an IPL program is built in a ROM for storing an application program (hereinafter referred to as an application ROM) in advance.

The procedure of changing the application program in the latter case is shown in the flowchart of FIG. As shown in the figure, in this case, if it is determined in step S1 that there is a program change request, the IPL program is transferred to the internal work RAM in step S2, and then the contents of the application ROM are erased in step S3. Further, in step S4, the changed application program is loaded via the input device, and sequentially written in the application ROM in step S5. This makes it possible to change the application program.

[0004]

PROBLEM TO BE SOLVED BY THE INVENTION Electrically erasable RO
In the conventional computer device which operates by writing the application program in M, when the system shown in FIG. 4 is used, it is necessary to have a dedicated ROM for storing the IPL program in addition to the normal application program, so the cost is high. There is a problem of rising. On the other hand, FIG.
In the case of this method, when the IPL program is transferred to the internal work RAM and some system abnormality occurs when the contents of the application ROM are erased and the program on the RAM is destroyed, the application program is transferred to the system. The problem is that you won't be able to load it again.

The present invention has been made in view of the above problems, and it is not necessary to have a dedicated ROM for storing an IPL program in a computer device that operates by writing an application program in an electrically erasable ROM. However, even if an abnormality such as the destruction of the IPL program occurs, the application program can be reloaded on the system.

[0006]

The computer device of the present invention is an electrically erasable ROM storing an application program and a control program for changing the application program, and an external memory at the same address as the system reset start address. And a means for suppressing output of a chip select signal for selecting the ROM when reading another written control program for changing the application program.

[0007]

When the external card storing the IPL program is connected to the connector of the computer device, a predetermined signal is supplied to the computer device via this connector. When the computer device is reset and activated in this state, the output of the chip select signal for selecting the built-in application ROM is suppressed, and the external card automatically outputs the I
The PL program is read and executed.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of a computer device of the present invention. As shown in the figure, an external IPL memory card can be connected to the computer device through a connector. A low active signal IPLON is supplied to this connector as a detection signal for determining whether or not an IPL memory card is connected. This signal is
It is input to the gate circuit shown in FIG. 2 together with the application ROM chip select signal for selecting the application ROM output from the CPU.

The gate circuit actively outputs the low active chip select signal ROS1 when the low active signal IPLON is at "H" level, but does not output the chip select signal ROS1 when the signal IPLON is at "L" level. It becomes active and the application ROM is not selected. That is, when the IPL memory card is connected, the application ROM is not selected and the IPL memory card is selected.

The program storage address on the IPL memory card is set to be the same as the reset start address. Therefore, when the IPL memory card is connected, the I supplied through the connector
Application ROM chip select signal is suppressed by PLON signal, and after hardware reset,
As shown in FIG. 3, the IPL program will be automatically started.

As described above, in the computer apparatus of the present invention, the memory cost for standardly incorporating the IPL program for changing the program inside is reduced, and the IPL program that has been generated in the conventional equipment is destroyed. This prevents the unchangeable state of the application program from being generated.

[0012]

The computer system of the present invention is an electrically erasable R storing an application program and a control program for changing the application program.
OM, and means for suppressing output of a chip select signal for selecting the ROM when reading another control program for changing the application program written at the same address as the system reset start address from the external memory. Is equipped with. Therefore, it becomes possible to reload the application program onto the system even if an abnormality such as destruction of the IPL program occurs, without having to have a dedicated ROM for storing the IPL program.

[Brief description of drawings]

FIG. 1 is a block diagram of a computer device of the present invention.

FIG. 2 is an application R of the computer device of FIG.
It is a circuit diagram of a gate circuit for suppressing the OM chip select signal.

FIG. 3 is an explanatory diagram of starting an IPL program by an external memory card.

FIG. 4 is a dedicated ROM for storing an IPL program
FIG. 6 is a block diagram of a computer device using the.

FIG. 5: R for storing application programs in advance
It is explanatory drawing at the time of building in an IPL program in OM.

6 is a flowchart showing a procedure for changing an application program in the computer device of FIG.

Claims (1)

[Claims] 1. An electrically erasable ROM in which an application program and a control program for changing the application program are stored, and another for changing the application program written from an external memory to the same address as the system reset start address. And a means for suppressing the output of a chip select signal for selecting the ROM when reading the control program.