Servicing Personal Computers, 3rd Edition

Microcomputer systems

7

Another, most useful, facility is associated with retaining the contents of the CPU registers

while a subroutine is being carried out. These can be 'pushed' onto the stack before making

the

call,

and then 'popped' off the stack on returning.

Instruction cycle

An instruction cycle can be divided into two distinct parts: the first is devoted to the fetching of

the instruction while the second

is

concerned with executing the desired operation. The

instruction cycle is thus also commonly referred to as the 'fetch/execute' cycle. During the first

state of the instruction cycle the CPU sends a memory read signal and the progra ...