Programming for Microprocessors

20

Basic

structure of a microprocessor

To read information back, the store is again supplied with an address.

It responds by producing the contents of the selected cell on its output

lines.

The operation is non-destructive; it does not alter any of the

information in the store.

The time needed to read or write information is known as the 'cycle

time'

of the store. In most present-day systems it is a fraction of a

microsecond. The phrase 'random access' is used because any cell in the

store can be reached equally quickly. The data is not ordered as it

would be on a magnetic tape.

ROM stands for read-only memory. As its name implies, the dat