Automobile Electrical and Electronic Systems, 5th Edition

Electrical and electronic principles

35

The accumulator now holds the running total. Steps 1 to 4 are the fetch

sequence and steps 5 to 10 the execute sequence. If the full fetch–execute

sequence above was carried out, say, nine times this would be the equivalent

of multiplying the number in the accumulator by 10! This gives an indication as

to just how basic the level of operation is within a computer.

Now to take a giant step forwards. It is possible to see how the microprocessor

in an engine management ECU can compare a value held in a RAM location

with one held in a ROM location. The result of this comparison of, say,

instantaneous engine speed ...