JPH03149620A - Microprocessor - Google Patents

Abstract

PURPOSE:To make it possible to mutually distinguish and execute cold start and warm start without adding a complex external hardware by switching the logical state of an input signal inputted from the external and changing the execution start address of an initializing program. CONSTITUTION:An address setting signal for setting up the execution start address of the initializing program at the time of turning on a power supply is formed from a start address forming circuit 1 based upon a reset signal obtained at the time of turning on the power supply. When a reset signal is inputted after turning on the power supply, the circuit 1 forms an address setting signal for setting up the execution start address of the initializing program corresponding to the logical state of an input signal applied from the external during the reset period after releasing the reset state. A program counter 2 sets up an initial value corresponding to each address setting signal to execute its corresponding initial program. Consequently, the cold start and the warm start can be distinguished from each other and executed without requiring the addition of a complex external hardware.

Description

[Detailed description of the invention] Industrial applications The present invention relates to microprocessors.

2. Description of the Related Art In general, in computer systems, the start of program execution by reset at power-on is called a cold start, and the start of program execution by reset after a cold start is called an ohm start. One of these cold starts is when the printer or CRT (Cathode) in the computer system is
(Ray Tube) A program is executed to initialize peripheral devices such as terminals, but in many cases this process only needs to be performed once when the power is turned on.This cold start initialization program is , Normal ROM (Read Only Memo
ry).

Therefore, in conventional microprocessors, in order to enable a warm start after a cold start, after initialization by a cold start, the reset address in the address map of the ROM is moved to another memory block (usually a floppy disk, etc.). The main program is loaded from the external storage device of RAM (Rand
External hardware is added to change the reset address written in o-^ccessNesiory)).

Problems to be Solved by the Invention In the conventional microprocessor described above, execution of 10 grams from a specific address is started by a reset input,
In other words, since the configuration is such that only a cold start is possible, external hardware must be added to distinguish between a cold start and a warm start. Therefore, if there are many reset conditions and you want to change the execution address according to those conditions, that is, if you want to selectively perform various types of warm starts in addition to cold starts, you need to add external hardware. The problem was that it was extremely complicated.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a microprocessor that can distinguish between a cold start and a warm start without requiring the addition of complex external hardware.

Means for Solving the Problems The present invention generates an address setting signal for setting the execution start address of an initialization program at power-on when a reset signal is received at power-on, and generates a reset signal after power-on. If the input signal is input from the outside during the reset period and is invalid during the reset period, at least one input signal is sampled during the reset period or at the timing of reset release, and the signal is input according to the logic state of the input signal. A start address generation circuit that generates an address setting signal to set the execution start address of the initialization program, and a program counter for instruction fetch that sets an initial value according to the address setting signal generated by the start address generation circuit. A microprocessor characterized by comprising:

According to the present invention, the start address generation circuit generates an address setting signal for setting the execution start address of the initialization program when the power is turned on in response to a reset signal when the power is turned on, and the program counter uses this signal. Initial values corresponding to are set and the initialization program is executed. For the reset signal that is input after the power is turned on, the start address generation circuit performs address setting to set the execution start address of the initialization program according to the logic state of the input signal applied from the outside during the reset period. A signal is generated after the reset is released, an initial value is set in the program counter according to the address setting signal, and the initialization program 11 is executed.

Solid Line Example FIG. 1 is a block diagram schematically showing the main parts of a microprocessor that is an embodiment of the present invention.

The start address generation circuit l sets an address setting signal for setting the execution start address of the initialization program when the power is turned on, and an execution start address of the initialization program when re-initialization is executed based on a switch input by the user. This circuit has the function of generating an address setting signal separately for the address setting signal.

That is, when receiving a reset signal at power-on, the start address generation circuit 1 generates an address setting signal for setting an execution start address for a cold start at the timing of canceling the reset, and generates a reset signal after a cold start. During the reset period, one or more input signals input for control purposes from outside the microprocessor (this input signal is invalid during the reset period) is sampled during the reset period or at the timing of reset cancellation. Then, after the reset is released, an address setting signal is generated for setting an execution start address for warm start according to the logic state of the input signal.

The program counter at the next stage is a circuit for fetching instructions, and sets an initial value according to the address setting signal generated by the start address generation circuit 1. R not shown
Give the address signal set to the OM (in which various programs including the initialization program are written).

ALU (^rithmetic Logic Uni
t; arithmetic logic unit) 5 is a circuit having the function of performing various arithmetic operations.

The register file 6 is a circuit for storing the results calculated by the ALU 5.

The instruction register is a register for receiving instructions read from the ROM and sent through the data path line 9, and temporarily holding them for execution. The decoder 8 is a circuit for decoding the instruction data held in the instruction register.

Next, an outline of the initialization 10-gram execution start operation in the microprocessor will be described.

When the reset signal is input to the start address generation circuit 1 when the power is turned on, after the reset is released, the start address generation circuit 1 outputs an address setting signal for setting the execution start address of the initialization program for cold start, and the program - In the counter 2, an initial value corresponding to this address setting signal is set, and the set address signal is sent to the ROM via the address latch 3 and address pass line 4, and a cold start is performed.

When a reset signal is given by a switch input by the user after the cold start, and at the same time, one or more specific control signals are given from outside the microprocessor as an input signal specifying execution of a predetermined reinitialization, the 178 start address The generation circuit 1 samples this input signal during the reset period or at the timing of reset cancellation, and after the reset is canceled, an address setting signal for setting an execution start address corresponding to the logic state of the input signal is sent from the start address generation circuit 1. Output. In the program counter 2, an initial value corresponding to this address setting signal is set, and the set address signal is transferred to the ROM via an address latch 3 and an address pass line 4.
and a corresponding warm start is performed.

In this way, the microprocessor can distinguish between a cold start and a warm start.

FIG. 2 is a block diagram showing another embodiment of the microprocessor of the present invention. In this embodiment, one or more specific data inputs provided by the user from the data input/output terminal 10 are used instead of the control signal as input signals for specifying reinitialization execution to be provided to the start address generation circuit l. This embodiment differs from the previous embodiment in that this is done as follows.

In FIG. 2, a data input/output buffer 11 is a register for temporarily holding data input/output from the data input/output terminal 10. The other circuit configurations and operations are the same as in the previous embodiment.

As described above, according to the microprocessor of the present invention,
Initialization 10 by switching the logic state of an input signal from outside the microprocessor that becomes invalid at reset.
Since the program execution start address can be changed, cold starts and warm starts can be distinguished and executed without adding any additional external hardware.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of the main parts of a microprocessor that is an embodiment of the present invention, and FIG. 2 is a schematic diagram of the main parts of a microprocessor that is another embodiment of the invention. FIG. 2 is a block diagram showing the configuration. 1...Start address generation circuit, 2...10 gram counter, 3...Address latch, 10-...Data input/output terminal

Claims (1)

[Claims] If a reset signal is received when the power is turned on, an address setting signal is generated for setting the execution start address of the initialization program for when the power is turned on; if a reset signal is received after the power is turned on, an address setting signal is generated. During the reset period, at least one input signal that is input from the outside and is invalid during the reset period is sampled during the reset period or at the timing of reset cancellation, and execution of an initialization program according to the logic state of the input signal is started. The present invention is characterized by including a start address generation circuit that generates an address setting signal for setting an address, and a program counter for instruction fetch that sets an initial value according to the address setting signal generated by the start address generation circuit. microprocessor.