MICROPROGRAM SEQUENCER ORGANISATION
A microprogram control unit consists of two parts : 1 ) Control Memory that stores the microinstructions 2) Associated circuits that control the generation of the next address . The address generation part is sometimes called a microprogram sequencer ,since it sequences the microinstructions in control memory . T ypical sequencer provides the following address-sequencing capabilities : 1.Increments the present address for control memory . Sequential access: The content of address register of the control memory (CAR) is incremented after execution of each micro-instruction . 2. Branches to an address as specified by the address field of the microinstruction. 3 . Branches to a given address if a specified status bit equal to 1. 4.Transfer control to a new address as specified by an external source . The external address transfers control to the first microinstruction in a microprogram . 5 .Support subroutine call ...