JPS605983B2 - Accumulator display method for 1-chip microprocessor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an accumulator display method for a one-chip microprocessor, in which the value of the accumulator can be displayed from outside the one-chip microprocessor that has an accumulator built into the chip, and the display operation is simple. It is an object of the present invention to provide an accumulator display method for a one-chip microprocessor in which the state of the one-chip microprocessor does not change before and after.

Conventionally widely used calculators consisted of individual parts such as accumulators and program counters, and because their signal lines were exposed outside the IC, it was possible to display the contents of the accumulator relatively easily. .

However, the one-chip microprocessor that has appeared in recent years is
One chip consists of an accumulator and a program counter.
The problem is that the contents of the accumulator cannot be easily known from the outside. Therefore, even in a one-chip microprocessor,
It was strongly desired to be able to display the contents of the accumulator. The present invention meets this need. The present invention will be described in detail with reference to a block diagram of one embodiment.

A is a one-chip microprocessor, and is formed of one chip. This one-chip microprocessor A is connected to a common path B.
A program counter memory 6, an instruction read-only memory 2, an accumulator display 8, and a program memory 7 are respectively connected to the . When the accumulator display request signal a is input to the accumulator display control circuit 1, the operation of the one-chip microprocessor A starts. Initially, the one-chip microprocessor A is in a stopped state, and enters a run state by the run request b signal b of the accumulator display control circuit 1. At this time, the program counter memory 6 stores the value of the program counter 5 before entering the run state. When entering the run state, the 1-chip microprocessor A attempts to read the instructions to be executed from the program memory 7, but at this time, the accumulator display control circuit 1 sends a read-out memory identification signal d to the 1-chip microprocessor A, and the program memory Instead of the instruction No. 7, the instruction from the instruction read-only memory 2 is forcibly read into the one-chip microprocessor A. The instruction in the instruction logic output memory 2 to be read into the one-chip microprocessor A is an accumulator display instruction, and the output instruction 1 is assigned to it.

This output command is composed of a part indicating that the command is an output command and a part indicating to which channel the output is to be made, and the output command for a certain channel is assigned as an accumulator display command. The one-chip microprocessor A that has read the accumulator display command executes the command and causes the accumulator display 8 to display the contents of the accumulator 4. During this time, the value of the program counter 6 has changed to a value larger than the initial value, but after executing the above instruction, the accumulator display control circuit 1
Then, the read end memory identification signal d is sent again to the 1-chip microprocessor A, and the 1-chip microprocessor A reads the jump instruction from the instruction output memory 2 and the jump destination address from the program counter memory 6. This jump instruction causes the one-chip microprocessor A to fetch the original value stored in the program counter memory 6 into the program counter 6. Next, the accumulator display control circuit 1 supplies the hole request signal c to the 1-chip microprocessor A, thereby bringing the 1-chip microprocessor A into a halt state. As described above, the accumulator display operation is completed. As the 1-chip microprocessor A, an 8-bit parallel CPU (80 eaves) manufactured by Intel is used, and the interrupt processing, which is the basic technology of the present invention, is described in the user's manual (MARCH I973REV3) distributed by the company. ), which also includes specific examples of signal input/output circuits.

That is, the one-chip microprocessor A is provided with an interrupt terminal that executes or stops execution of an instruction in response to an external interrupt request, and after applying an interrupt request signal to the interrupt terminal of the CPU, the following By inserting a preset instruction in a fetch cycle, the desired instruction can be executed, and after applying an interrupt request signal to the interrupt terminal of the CPU, a halt instruction can be inserted. This will allow you to stop execution. Therefore, if the fetch memory identification signal d is used as an interrupt request signal for the 1-chip microprocessor A, instead of the program from the program memory 7, the memory 2 for fetching the instruction will be used as the jump destination of the jump instruction and the program counter setting switch 6. The operation of reading an address into the one-chip microprocessor A can be easily realized. Further, the accumulator display control circuit 1 can be understood as a type of timing control circuit, and when the accumulator display request signal a is input, it generates the run request signal b, and then the one-chip microp. At the timing when processor A is about to fetch an instruction, it generates a read end memory identification signal d, and immediately after the one-chip microprocessor A executes an output command, which is an accumulator display command, it generates a read end memory identification signal d again.
It can be said that this is a timing control circuit configured to generate a hole request signal c immediately after the one-chip microprocessor A executes a jump instruction. The specific configuration can be freely designed by those skilled in the art so as to realize the above functions based on the user's manual. As described above, the present invention forcibly loads the accumulator display command from the instruction read memory into the one-chip microprocessor in advance of the command from the program memory by the accumulator display control circuit, and this command causes the accumulator display to be displayed. Since the contents of the accumulator are displayed on the body, the program memory value can be viewed and the efficiency of program depacking can be improved. Since the 1-chip microprocessor executes a jump instruction to the address of the stored value and fetches the original value of the program counter, the program counter that has changed from the value before the accumulator display operation is The value is returned to the original value, and the 1-chip microprocessor has executed only the display operation of the accumulator.Furthermore, since the 1-chip microprocessor is set to stop immediately after executing this jump instruction, the 1-chip microprocessor is stopped. This is similar to displaying the contents of the accumulator while it is in the stopped state, and in the end it is possible to know the contents of the accumulator even when it is stopped, further improving the efficiency of program depacking and greatly improving the operating functions of the 1-chip microprocessor. It has the advantage of being able to

[Brief explanation of the drawing]

The drawing is a block diagram of one embodiment of the present invention, in which A is a one-chip microprocessor, 1 is an accumulator display control circuit, 2 is a memory for reading instructions only, 4 is an accumulator, 5 is a program counter, and 6 is a program counter. Memory, 7 is a program memory, and 8 is an accumulator display.

Claims (1)

[Claims] 1 Combine the accumulator and program counter into one L
In the 1-chip microprocessor in the SI chip, the accumulator display control circuit forcibly loads the accumulator display command from the instruction read-only memory into the 1-chip microprocessor, giving priority to the command from the program memory. Display the contents of the accumulator on the accumulator display body according to the command,
Then, the 1-chip microprocessor executes a jump instruction to the address of the value previously stored in the program counter memory, fetches the original value in the program counter, and immediately after executing this jump instruction, the 1-chip microprocessor An accumulator display method for a one-chip microprocessor, which is characterized by bringing the setter into a stopped state.