Question

9. List different blocks in a micro-programmed control unit? Compare and contrast Hardware vs. Microprogrammed CU ? In a microprogrammed control unit, 16 micro-operations are needed. Number of conditions to be checked is 4 and size of microprogram is 2k. Find horizontal format for a microinstruction?

Answer 1

THE MICROPROGRAMMED CONTROL UNIT:

The logic of the control unit is specified by a micro program. A microprogram is also called firm ( midway between the hardware and software). it consists of:

(a) one or two micro operations to be executed,and

(b) the information about the micro instruction to be executed next .

The general configuration of the micro programmed control unit:

The micro instructions are stored in control memory. The address register for control memory contains the address of the next instruction that is to be read .the control memory buffer register receives the micro instruction that has been read.the micro instruction execution primarily involves the generation of desired control signals and signals used to determine the next instruction to be executed .the sequencing logic section loads the control memory address register .it also issues a read command to control memory . the following fuctions are performed by the micro program control unit.

1. The sequence logic unit specifies the address of the control memory word that is to be read, in the address of the control memory .it also issues the read signal.

2.The desired control memory word is read in to control memory buffer register .

3.The content of the control memory buffer register is decoded to create control signals and next address information for the sequence logic unit.

4.The sequencing logic unit finds the address of the next control word on the basis of the next address information from the recorder and ALU flags .

This decoder translates the opcode of the IR into a control memory address .

  

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COMPARE AND CONTRAST HARDWIRE VS.MICROPROGRAMMED CONTROL UNIT:

The main difference between haradwired and microprogrammed control unit and is that a hardwired control unit is a seqencial circuit that generates control signal while a microprogrammed control unit is a unit with micro instruction control memory to generate control signal.

The processor or the cpu is the main compliment of the computer that handles most of the tasks . it consists of main two sub systems,arithmatic and logic unit and the control unit(cu).ALU handles the mathmatical and logical operations while cu sends timing and control signals to the other units to syncronize the tasks.The control unit can either be hardwired or microprogrammed.hardwired control units are difficult to modify ,decode and implement ,but execites operations much faster.on the other hand ,microprogrammed control unit for easier to modify ,decode ,implement and capable of handling complex instuctions .