User’s Manual 111
11. TIMERS
There are two timers—Timer A and Timer B. Timer A is intended mainly for generating
the baud clock for the serial ports, a periodic clock for clocking parallel ports D and E, or
for generating periodic interrupts. Timer B can be used for the same functions, but it can-
not generate the baud clock. Timer B is more flexible when it can be used because the pro-
gram can read the time from a continuously running counter and events can be
programmed to occur at a specified future time.
Figure 11-1 shows a block diagram of Timers A and B.
Figure 11-1. Block Diagram of Timers A and B
A1
perclk
/2
A4
A5
A6
A7
Timer A System
10-bit counter
match reg
match reg
compare
Timer B System
match preload
match preload
10 bits
Timer_B1
Timer_B2
f/8
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