Hardware Reference
In-Depth Information
Figure 1.3
Microcomputer system with bus expansion capability
Photo 1.4
A typical ISA expansion card which provides two serial and two
parallel ports
Microprocessor operation
The majority of operations performed by a microprocessor involve the move-
ment of data. Indeed, the program code (a set of instructions stored in
ROM or RAM) must itself be fetched from memory prior to execution. The
microprocessor thus performs a continuous sequence of instruction fetch and
execute cycles. The act of fetching an instruction code or operand or data value
from memory involves a read operation whilst the act of moving data from the
microprocessor to a memory location involves a write operation.
