JPS61231633A - Microprocessor - Google Patents

Abstract

PURPOSE:To facilitate a test by inserting a microprogram for check to an optional part of the microprogram. CONSTITUTION:In supplying a branch request signal to a terminal 10, a microprogram muPG branch control circuit 8 applies a branch request signal to a branch address register 7, a multiplexer MPX 2, a mu address register 3, an incrementary 4 and a mu address stack register 11. The MPX 2 selects the branch address stored in the register 7 and applies it to the register 3. The register 3 saves the address data stored just before to the register 11, stores the branch address and applies it to the muROM 5. Thus, the internal check PG for the mu processor is read from the ROM 5 and the internal data of an ALU 13 and the internal data of the data register 12 are read to the bus 14, outputted externally via the terminal 15 to check the internal state.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a microprocessor, and particularly to a microprocessor using a microprogram control method.

(Prior art and its problems) In recent years, with advances in semiconductor technology and market demands, microprocessors have become faster and more sophisticated.

However, the demand for higher functionality has led to the complexity of the internal circuits of microprocessors, which is one reason for the length of circuit design and evaluation.

By the way, high-performance microprocessors often use a microprogram control method, which is advantageous for design changes, etc., but is disadvantageous from the standpoint of verification and testability of a single function. This is because the internal operations of a microprocessor using a microprogram control system are defined by the microprogram stored in the microprogram ROM, so whether instructions are executed normally depends on the operation of the microprogram ROM. Because it has to be investigated.

Conventionally, microprocessors using microprogram control have generated microprogram addresses using all of the following three methods.

■ Generate an address using part or all of the instruction code.

■ Add 1 to the current microaddress register value to make the next address.

: 1 ■ Generate the next address using part or all of the current microcode.

The above address generation specifications (1), (2), and (2) will be explained with reference to Figure 2, which is a block diagram of the main parts of a conventional microprocessor.

First, the instructions taken in by the microprogrammer are written into the instruction register.

The output of the instruction register is then passed through multiplexer 2 and written to microaddress register 3.

The output of micro address register 3 is micro ROM 5
The microprogram corresponding to the instruction code that is input to is output to microat)'output 7[6. This is the above item (■).

Further, the output of the microaddress register 3 is connected to an incrementer 4 and updated to designate the next microROM address, which is then written to the microaddress register 3. This is the above item (■).

Furthermore, when a branch instruction is executed in the microprogram to change the flow of the microprogram, the output of the microcode output line 6 is passed through the multiplexer 2t- to rewrite the microattribute and address registers 3. This is the above item (■).

As long as the addressing method described above is used, the internal operation is determined only by instructions given from the outside, and even if an abnormality occurs in the result of instruction execution, it is extremely difficult to investigate the cause. Particularly when one instruction is implemented using microinstructions that span several tens of steps, there is a problem in that even if an abnormality occurs during the execution of a microprogram, it is nearly impossible to investigate the cause.

(Object of the Invention) An object of the present invention is to provide a microprocessor with improved testability by allowing a testing microprogram to be inserted into any part of the microprogram.

(Means for Solving the Problems) The device of the present invention is one of the microprogram control systems. a data selection means for selecting data to be supplied to the address register; and a specific address data storage that can be stored in accordance with a specific address command in the storage means of the specific microprogram. means for selecting the specific address data stored in the specific address data storage means by the data selection means in response to an external signal, and writing the specific address data into the address register. and control means for reading out the specific microprogram from the storage means.

(Example) First, embodiments of the present invention will be described with reference to the drawings.

FIG. 811 is a block diagram showing essential parts of an embodiment of the present invention. , the microprocessor of FIG. 1 has a large register 1, which temporarily stores instructions.

Multiplexer 2 selects one t' from multiple inputs
, a micro address register 3 that temporarily stores the address data of the micro IILOM 5, an incrementer 4 that adds 1t to the supplied address, and a micro R that is a read-only memory that stores micro programs including a test micro program. , OM5, a branch address register 7 that stores address data of a location where a microprogram for inspection is stored, a microprogram branch control circuit 8 that controls branching of the microprogram, and a microprogram that temporarily stores address data to be saved. Address stack register 11 and data register 1
2 and an arithmetic unit (ALU) 13.

Instruction register 1. Multiplexer 2. Micro address register 3. The operation of executing the microprogram by the incrementer 4 and the micro ROM 5 is the same as the conventional operation described above with reference to FIG. 2, and the description thereof will be omitted since it is redundant.

When it is desired to perform an internal inspection of the microprocessor at any point during the execution of a certain microprogram, a branch request signal is supplied to the terminal 10 in FIG.

Microprogram branch control circuit 8 supplies this branch request signal to branch address register 7, multiplexer 2, microaddress register 3, incrementer 4, and microaddress stack register 11.

This causes multiplexer 2 to use branch address register 7.
The branch address stored in the micro address register 3 is selected and supplied to the micro address register 3. The micro address register 3 saves the address data stored until just before into the micro address stack register 11, stores the supplied branch address, and supplies it to the micro R and OM 5.

As a result, a program for internal inspection of the microprocessor is read from the micro ROM 6, and the internal data of the ALU 13 and the internal data of the data register 12 are read to the internal data bus 14 and output to the outside via the output terminal 15i, thereby checking the internal state. Can be inspected.

When the branch request signal supplied to the terminal 10 is made inactive, the microaddress stack register 11
By incrementing the address data immediately before the branch stored in the incrementer 4 by 1 and setting it in the microaddress register 3 via the multiplexer 2, the original microprogram before the branch can be continued.

As described above, according to this embodiment, the internal state of the microprocessor at any point in the microprogram can be inspected.

In this embodiment, the branch address of the branch address register is fixed, but it is obvious that by changing this, the test program can be changed and various tests can be performed.

(Effects of the Invention) The present invention has the advantage that by inserting a microprogram for internal inspection into any position of the microprogram, testing of the microprocessor can be facilitated and circuit design and evaluation can be made more efficient. There is.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
The figure is a block diagram showing a conventional example. 1... Instruction register, 2...
...Multiplexer, 3...Micro address register. 4...Incrementer, 5...Micro OM, 6...Micro code output line, 7...
...Branch address register, 8...Microprogram branch control circuit, 9...Branch control signal, 10...Microprogram branch request input, 11... ...Micro address stack register, 12...Data register, 13...
・ALtJ, 14...Internal data bus, 15.
...Data terminal.

Claims (2)

[Claims] (1) In a microprocessor using a microprogram control system, a storage means for storing a plurality of microprograms including at least a specific microprogram, an address register for storing address data to be supplied to the storage means, and supply to the address register. data selection means for selecting data to be selected; specific address data storage means capable of storing a specific address in the storage means of the specific microprogram according to a command; and data selection means for selecting the specified data in response to an external signal. A microprocessor comprising control means for selecting the specific address data stored in the address data storage means, writing the specific address data in the address register, and reading out the specific microprogram from the storage means. (2) The specific microprogram is a test microprogram for testing the internal state of the microprocessor, and the test microprogram read by the control means tests the internal state of the microprocessor. A microprocessor according to scope (1).