JPH06348504A - Microprocessor system - Google Patents

Abstract

PURPOSE:To provide a microprocessor system which abolishes a boot ROM and can freely alter a processing program. CONSTITUTION:This microprocessor system is equipped with a detachable memory card 4 stored with a start program and the processing program, a nonvolatile memory 5 which is assigned to a different area in the same address space as the memory card 4, a state setting switch 7 for setting a start mode, and an address decoding means 6 which replaces the memory card area and nonvolatile memory area in the address space with each other according to the start mode. In memory card start mode, the start program is executed to transfer the processing program from the memory card 4 to the nonvolatile memory 5 and then the system is placed in nonvolatile memory start mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microprocessor system, and more particularly to a microprocessor system which starts a program without using a boot ROM.

[0002]

2. Description of the Related Art In a Neumann type computer including a microprocessor, a program to be executed at reset must exist in a storage space. Usually, in a small-scale circuit using a microprocessor, an EPROM or mask ROM in which a processing program is written in advance (hereinafter referred to as ROM) is mounted on the circuit,
The first instruction fetch address output by the microprocessor after reset is assigned to the ROM.

For example, LEDs are arranged vertically and horizontally to form a display screen, and LEDs for displaying characters, figures, etc. on the screen.
In the display device, the program for controlling the display is EP
The display data is stored in each of the non-volatile memories in the ROM, and when the power is turned on, the display control program reads the display data and sequentially displays the display data. This display data is changed according to the application, and is input by a memory card or transferred and input by using the communication function.

Such an LED display device often requires special specifications such as display configuration and function depending on the place of use. In this case, the EPROM mounted on the circuit is exchanged to change the display program, which is a difficult method.

On the other hand, when it is desired to freely change the processing program, a method is adopted in which the processing program is loaded by the start-up program, control is passed to the processing program, and the control program is executed. That is, a ROM in which a startup program is written (which is called a boot ROM) is mounted on a circuit, and a processing program is prepared in an external storage such as a floppy disk or a hard disk (hereinafter referred to as a disk). Then, after the processing program is read from the disk by the start-up program executed at the time of resetting and loaded on the memory, control is passed to this processing program.

[0006]

However, in the method using the boot ROM, a short boot program for starting must be mounted in the circuit without fail.
The focus of OM production has shifted to large-capacity ROMs, and production of small-capacity ROMs suitable for boot programs is often discontinued. For this reason, it is difficult to obtain a small-capacity ROM, and there is a problem that production is hindered due to a bottleneck of parts.

Further, when the production amount of the small-capacity ROM is reduced and the ROM is handled as a maintenance part, there is a problem that the price of the part is increased and the manufacturing cost is increased.
Further, mounting the boot ROM has a problem in that the number of circuit components is reduced and the product is reduced in size and weight.

In view of the above problems, an object of the present invention is to provide a microprocessor system in which the boot ROM is eliminated and the processing program can be freely changed.

[0009]

In order to solve the above problems, the present invention has the following constitution. That is, the present invention provides a removable memory card in which a boot program and a processing program are stored, a non-volatile memory allocated to different areas of the same address space as the memory card, and a status setting for setting a boot mode. A switch and an address decoding means for exchanging the memory card area and the non-volatile memory area in the address space based on the starting mode set in the state setting switch are provided, and the state setting switch is set to the memory card starting mode. The first command address after reset is assigned to the memory card, the boot program stored in the memory card is executed, the processing program stored in the memory card is transferred to the non-volatile memory, and the status setting switch is set after the processing program transfer is completed. To switch to non-volatile memory start mode The Rukoto, which in the subsequent reset a microprocessor system and executes a processing program stored in the nonvolatile memory card.

[0010]

After the reset, the microprocessor reads from the instruction at the predetermined address and executes it. Now, assume that this predetermined address is address 0. In the address space of the microprocessor, at least a nonvolatile memory and a removable memory card are arranged.

A state setting switch and an address decoder are provided to replace the nonvolatile memory and the memory card in the address space. The status setting switch is O
There are two states, N and OFF. For example, assume that the ON state is assigned to the nonvolatile memory start mode and the OFF state is assigned to the memory card start mode.

The address decoder decodes the upper bits of the address line of the microprocessor to generate a chip select (hereinafter abbreviated as CS) signal of the non-volatile memory and a CS signal of the memory card. In addition, the address decoder, based on the ON / OFF state of the state setting switch, CS of the nonvolatile memory and C of the memory card.
Swap S and. That is, the status setting switch is ON
In the case of (non-volatile memory start mode), the address area including address 0 is assigned to the non-volatile memory, and when the status setting switch is OFF (memory card start mode), the address area including address 0 is stored in the memory. Assigned to cards.

The method of starting the microprocessor system having the above configuration is as follows. First, the memory card in which the startup program and the processing program are written is inserted, and the state setting switch is set to OFF (memory card startup mode). Next, when the power is turned on, the reset circuit operates, and when the microprocessor executes the cycle for fetching the instruction at address 0, the memory card is accessed and the activation program is executed.

Then, the processing program stored in the memory card is written in the non-volatile memory in accordance with the startup program. When writing is completed, it may be notified by an appropriate method. Next, the operator turns off the power once
Then, the state setting switch is switched from OFF to ON to set the nonvolatile memory starting mode. After that, when the power is turned on, the processing program is executed from the address 0 of the nonvolatile memory after the reset of the microprocessor. As described above, the boot ROM
The microprocessor system can be brought up without using.

[0015]

An embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of a microprocessor system according to the present invention. In the figure,
The microprocessor 1 has an 8-bit data width and 16-bit data width.
It has an address width of bits. A memory card 4 and a non-volatile memory 5 are connected to the data bus 2 and the address bus 3 of the microprocessor. The address decoder 6 is connected to the upper bits (A12 to A15) of the address bus.

The status setting switch 7 has one terminal 7-1.
Is grounded, and the other terminal 7-2 is connected to the pull-up resistor 8. The terminal 7-2 of the state setting switch is connected to the SW input of the address decoder 6. Further, the terminal 7-2 of the state setting switch is connected to the input of the tri-state buffer 9 and the R of the address decoder 6 is connected.
The output of the tri-state buffer 9 controlled by the EAD output is output to an appropriate bit position of the data bus 2.

The memory card 4 is constructed so that it can be attached to and detached from the microprocessor system.
The starting program is stored from the address 0, and the processing program is stored subsequently. Non-volatile memory 5
As is well known, is a memory in which written data is not erased even when the power is turned off.

The memory card 4 and the non-volatile memory 5 are connected to the lower bits A0 to A11 of the address bus. Further, a data strobe signal (hereinafter abbreviated as DS) and a read / write signal (hereinafter abbreviated as R / W)
Are connected to the memory card 4 and the non-volatile memory 5 from the microprocessor 1 in the same manner as a normal microprocessor.

The address decoder 6 is connected to DS and R / W from the microprocessor 1 similarly to the memory. Further, the address decoder 6 decodes the upper bits of the address, sends chip select (hereinafter abbreviated as CS) CS1 and CS2 to the memory card 4 and the nonvolatile memory 5, and then sends an acknowledge signal (hereinafter referred to as an acknowledge signal) to the microprocessor 1. , DAK) is connected to the signal line.

FIG. 2 shows ON / OF of the status setting switch 7.
It shows a memory map corresponding to the F state. Figure 2
The state in which the state setting switch 7 shown in (a) is OFF is the memory card starting mode, and the address 0000
_{(H) to} 3FFF _(H) are assigned to the memory card 4,
The addresses 9000 _{(H) to} CFFF _(H) are assigned to the non-volatile memory 5. A state in which the state setting switch 7 shown in FIG. 2B is ON is a non-volatile memory starting mode, and addresses 0000 _{(H) to} 3FFF _(H) are assigned to the non-volatile memory 5 and address 9000 _{( H). H)} ~ CF
FF _(H) is assigned to the memory card 4.

The address decoder 6 selects the chip select C of the memory card 4 based on the upper address bits (A12 to A15) and the status signal SW of the status setting switch 7.
S1 and the chip select CS2 of the non-volatile memory 5 are created to realize the above address arrangement. A detailed circuit example of this decoding is shown in FIG. In FIG. 3, 101 is 4
Bit decoder, 102 and 103 are OR circuits, 104
Is a circuit for switching CS1 and CS2 according to SW.

Next, the operation of this embodiment will be described. First, with the state setting switch 7 in the OFF state, the memory card 4 is mounted and the power is turned on. The memory card 4 stores a start program from address 0 in advance,
Following this, a processing program is stored. When the reset is completed, the microprocessor 1 starts execution from the instruction stored in the address 0, so that the startup program is executed. Then, according to the processing of the startup program,
The processing program is read from the memory card 4 and written in the nonvolatile memory 5.

When the writing is completed, control is passed to the processing program and a part of the processing program is executed. The processing program reads the status setting switch assigned to the specific address of the memory, and the status setting switch 7 turns off.
When it is confirmed that it is FF, it knows that it is in the memory card activation mode and notifies the operator of the completion message.

When the operator reads the completion message, the power is turned off and the state setting switch 7 is turned on. As a result, the address arrangement shown in FIG. 2B is obtained, and thereafter, when the power is turned on, the execution after the reset of the microprocessor 1 is performed from the head address of the nonvolatile memory 5. The processing program confirms the state setting switch 7 and knows that it is in the non-volatile memory starting mode because it is turned on, and the normal processing program can be executed to fulfill the function of the device.

Further, after removing the memory card in which the boot program and the processing program have been written, a memory card for data can be inserted to be used as a data medium. The non-volatile memory includes SRAM backed up with a battery and flash memory, but a flash memory that does not require battery backup is more preferable. As described above, the same function as the boot ROM can be realized without using the boot ROM.

The above embodiments do not limit the present invention. For example, the address arrangement and the configuration of the address decoder are merely examples, and various changes can be made.

[0027]

As described above, according to the present invention, by eliminating the boot ROM, the EPROM occupying a relatively large area among the surface mount components is eliminated, and the device can be miniaturized. There is. Moreover, since a small capacity ROM that is difficult to obtain is not used, there is no bottleneck of parts,
There is an effect that a device using a microprocessor can be smoothly produced.

Further, after the processing program is written in the non-volatile memory, the processing program can be directly executed after the power is turned on, and it is not necessary to execute the startup program written in the boot ROM. The effect is that it can be shortened.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of an embodiment according to a microprocessor system of the present invention.

2 shows a memory map of an embodiment, FIG.
FIG. 2B shows a state when the state setting switch is OFF.
Indicates that the state setting switch is ON.

FIG. 3 is a detailed circuit diagram of a main part of an address decoder.

[Explanation of symbols]

1 Microprocessor 2 Data bus 3 Address bus 4 Memory card 5 Non-volatile memory 6 Address decoder 7 State setting switch 8 Pull-up resistor 9 Tri-state buffer DS: Data strobe signal R / W: Read / write signal DAK: Acknowledge signal SW: Signal indicating the ON / OFF state of the status setting switch READ: Signal for reading the status setting switch

Claims (1)

[Claims] 1. A removable memory card in which a boot program and a processing program are stored, a non-volatile memory allocated to different areas of the same address space as the memory card, and a status setting switch for setting a boot mode. And an address decoding means for exchanging the memory card area and the non-volatile memory area in the address space based on the start mode set in the state setting switch, and setting the state setting switch in the memory card starting mode. The first instruction address after reset is assigned to the memory card, the boot program stored in the memory card is executed, the processing program stored in the memory card is transferred to the non-volatile memory, and the status setting switch is pressed after the processing program transfer is completed. Switch to non-volatile memory start mode And a microprocessor system and executes a processing program stored in the nonvolatile memory card in which the subsequent reset.