In this section, there are two ways to take advantage of this redundancy to reduce the number of microinstructions needed by the control unit. The first method uses microsubroutines to combine repeated micro-operations into a single block of micro-instructions, which are accessed by two or more execute routines. The other ... Read More

In vertical microcode, each microinstruction is encoded i.e., the bit field can pass through intermediate combinatory logic which in turn creates the actual control signals for internal CPU components (ALU, registers, etc). In vertical microcode, the micro-operations are grouped into fields such that no more than one micro-operation in a ... Read More

In horizontal microcode, each micro-operation is represented by one bit in each microinstruction. Horizontal microcode is generally included in a fairly wide control save it is not exceptional for each work to be 56 bits or more. On each click of a sequencer clock, a microcode word is read, decoded, ... Read More

The microprogram sequence is a general-purpose building block for the microprogrammed control unit. The main objective of the microprogram sequencer is to demonstrate an address to the control memory so that microinstruction can be read and executed. The next address logic of the sequencer decides the particular address source to ... Read More

A microsequencer is also designed as a finite state machine. Consider the generic microsequencer shown in the figure. The register stores a value that corresponds to one state in the CPU’s state diagram. It serves as the address that is input to the microcode memory. This memory outputs a microinstruction, ... Read More

The status register comprises the status bits. The bits of the status register are modified according to the operations performed in the ALU. The figure displays a block diagram of an 8-bit ALU with a 4-bit status register.If the end carry C8 is 1, then carry (C) is set to ... Read More

Instructions of the computer are always stored in consecutive memory locations. These instructions are fetched from successive memory locations for processing and executing.When an instruction is fetched from the memory, the program counter is incremented by 1 so that it points to the address of the next consecutive instruction in ... Read More

Data manipulation instructions have computational capabilities. They perform arithmetic, logic, and shift operations on data.There are three types of data manipulation instructions are as follows −Arithmetic InstructionsArithmetic operations include addition, subtraction, multiplication, and division. Some computers provide instructions only for addition and subtraction operations and generate multiplication and division operations ... Read More

Data transfer instructions transfer the data between memory and processor registers, processor registers, and I/O devices, and from one processor register to another. There are eight commonly used data transfer instructions. Each instruction is represented by a mnemonic symbol.The table shows the eight data transfer instructions and their respective mnemonic ... Read More

Instructions in a computer can be of multiple lengths with a variable number of addresses. The various address fields in the instruction format of a computer vary as per the organization of its registers. It depends on the multiple address fields the instruction can be categorized as three address instructions, ... Read More