DE4026871A1 - Microprogrammable processor e.g. for data processing system - has microprogram store subdivided into read-only memory area and random access memory area - Google Patents

Abstract

The microprogrammable processor (control unit) includes a microprogram store which is subdivided into a read-only memory (ROM) area and a random access memory (RAM) area. Both these stores are simultaneously addressed with the content of the microprogram counter. A multiplexer (MUX 3) is used in the selection of one of the two stores by using control vectors read from the stores themselves, and the selection signal (SS2) used for determing which of the two command sets is selected, is held in the register (REQ 20). ADVANTAGE - System can function simultaneously with number of command sets.

Description

The invention relates to a microprogrammable control unit for a micro-programmable information processing device.

It is known to control units for information processing devices using hard-wired logic. Such control units point however, the disadvantage that their function can no longer be changed can.

Micro-programmable control units are therefore known Function is determined solely by the content of a memory, so that the function of this control unit in a simple manner Changing the memory content can be changed.

Depending on the form of storage of the tax information under one differentiates between horizontal and vertical microcode.

With the horizontal microcode, the individual tax information ions stored uncoded in the memory. As for the uncoded Storage a memory of a very large word width is needed however, this form of coding is not of great practical importance acquired.

It is therefore to reduce the size of the word width of the memory the vertical microcode is known, the control information encoding stored in the memory and the control information after reading the Memory is decoded using a decoder.

However, the vertical microcode has the disadvantage that in general for the execution of a macro instruction more micro instructions are required than for horizontal microcode.

It is therefore known that the advantages of both codes in the to combine so-called two-stage microcode. Here exist the two levels of the vertical microcode and the horizontal Nanocode.  

To a micro-programmable information processing device Being able to use it universally becomes the control unit of such a system Information processing device generally with a unspecialized instruction set. This allows everyone Information processing devices with the same programs, in particular the same operating system, operated, whereby the effort involved in creating these programs is reduced.

Due to the unspecialized interpretation of the instruction set, however Performance of such an information processing device cannot be fully exploited. Command set is still on adapted to its specific application, the existing ones can Programs such as the operating system are no longer used will.

The present invention is therefore based on the object micro-programmable control unit for a micro-programmable Information processing device to specify which one is the same enables timely work with a large number of instruction sets and thereby giving the user the use of an application-specific Instruction set and the simultaneous use of a standard Operating system.

According to the invention, this object is achieved by a micro-programmable Control unit solved, which the characteristic features of the Claim 1 has.

Embodiments and advantages of the invention are in the subclaims, shown in the description and in the drawing.

Exemplary embodiments are shown in the drawing and are shown in following described in more detail. In

Fig. 1 is an inventive micro-programmable control unit and in

Fig. 2 shows a preferred embodiment of the control unit according to the invention.

In Fig. 1 a block diagram for one embodiment is shown with horizontal microcode. The microprogram memory has a size that enables a large number of different instruction sets to be stored.

The microcode stored in this memory is divided into three Fields on.

A condition field (SEL 1 ) is used to select the external condition EB 1 by means of a multiplexer (MUX 1 ) in the event of a conditional branch in the microinstruction. Another field is provided to store the uncoded control information. The last field is used to form the next address (FA 1 ) in the event of a branch. For this purpose, in the event of a conditional branching, the micro program counter µPC is loaded by means of the signal L 1 with the following address FA 1 .

If the microprogram counter is neither with a subsequent address nor with an external address (EA) is loaded, the addressing of the next control vector of the microprogram memory Micro program counter incremented.

The address of the microprogram memory is composed of the content of the microprogram counter and the content of register REG 10 . As a result, a memory area can be selected using the register REG 10, as a result of which this register enables switching between a plurality of command sets.

According to a preferred embodiment, the microprogram memory in a non-volatile (ROM) and a writable memory area (RAM) divided.

For this purpose, a micro program memory for a variety of instructions sets also as a plurality of memories for one instruction set each will be realized.

The block diagram shown in FIG. 2 shows an exemplary embodiment with two memories, with one of these memories being designed as a non-volatile memory (ROM) and the other memory being a writable memory (RAM).

Here, both memories are addressed simultaneously with the content of the micro program counter. One of the two control vectors read from the memories is selected by means of the multiplexer MUX 3 , the selection signal AS 2 for determining which of the two command sets is selected is stored in the register REG 20 .

The multiplexer MUX 3 can be implemented in a known manner by using memories with open collector or three-state outputs, only the output drivers of one of these memories being released.

For the operation of a micro-programmable according to the invention Control unit is provided in the non-volatile memory area to store a special instruction set for operating system applications and a special instruction set in the writable memory area for the respective application of the information processing device to load.

When the reset signal of the information processing is activated the register for recording the information, which of the command sets is selected with a defined value pre-assigned, whereby the one stored in the non-volatile memory area Command set is selected.

According to a preferred embodiment of the control unit is used as a register for storing the information of which of the command sets is selected one or more bits of the status register of the information processing device used.

This has the advantage that the Information about which of the command sets was used automatically is saved with the content of the status register. Furthermore, without losing time by setting the interrupt lock to one defined command set are switched, which is the advantage can be achieved that the interrupt service routine a defined Command set received.

If you want to switch to a different command set, do so all that is required is the content of the register, which the Information contains which of the instruction sets is used changed to become.

However, it should be ensured that during the execution of the No commands to change this register at the moment of switching undefined states occur in the control unit.  

Two measures are possible for this:

One way is to keep the register content until completion the command execution in an additional register to save.

The other option is to use the commands to change the To code the contents of the register in the same way for all instruction sets, so that the Control unit can be switched during the execution of the command.

In a multi-tasking system, the instruction sets can also be dynamic can be reloaded if the number of required command sets is Number of available memory areas exceeds. It is here expedient, the allocation of the information processing device to the individual processes depending on the instruction set used perform.

Claims (10)

1. Micro-programmable control unit for a micro-programmable information processing device, characterized in that the micro-program memory is designed to hold a large number of different instruction sets and that a register (REG 10 ) is provided for storing the information as to which of the instruction sets is used. 2. Control unit according to claim 1, characterized in that the microprogram memory is designed as an independent memory, wherein all these memories are acted upon simultaneously with the same address and that an additional multiplexer (MUX 3 ) is provided for selecting the content of one of these memories. 3. Control unit according to claim 2, characterized in that the Multiplexer as parallel connection of memories with open collector or three-state outputs. 4. Control unit according to one of claims 1 to 3, characterized in that the storage of the information of which of the instruction sets is used in the status register of information processing direction. 5. Control unit according to one of claims 1 to 4, characterized in that at least one of the instruction sets in a non-volatile Memory area (ROM) is available. 6. Control unit according to one of claims 1 to 5, characterized in that when the reset signal is activated, the control unit on the non-volatile memory area (ROM) is switched. 7. Control unit according to one of claims 1 to 6, characterized by an additional register for delaying the selection signal for switching the control unit (z. B. AS 1 ) until the end of a command execution. 8. Method for operating a micro-programmable control unit according to one of claims 1 to 7, characterized in that with setting the interrupt block to a defined one at the same time Instruction set is switched.   9. Method for operating a micro-programmable control unit according to one of claims 1 to 6, characterized in that the Commands to change the register containing the information which of the instruction sets is used for all instruction sets be coded immediately. 10. Method for operating a micro-programmable control unit according to one of claims 1 to 7, characterized in that the Allocation of the information processing device to the individual Processes depending on the command set currently used and the instruction set used by the processes.