10.6 Synchronization of Free-Running Timers 1 to 3
10.6.1 Synchronization after a Reset
The three free-running timer channels are synchronized at a reset and remained synchronized
until:
the clock source is changed;
FRC contents are rewritten; or
an FRC is cleared.
After a reset, each free-running counter operates on the /4 internal clock source.
10.6.2 Synchronization by Writing to FRCs
When synchronization among free-running timers 1 to 3 is lost, it can be restored by writing to the
free-running counters.
Synchronization on Internal Clock Source:
When an internal clock is selected, free-running
timers 1 to 3 can be synchronized by writing data to their free-running counters as indicated in
table 10-4.
Table 10-4 Synchronization by Writing to FRCs
Clock Source
/4
/8
/32
m, n: Arbitrary integers
Write Interval
4n (states)
8n (states)
32n (states)
Write Data
m
m + n
m + 2n
(FRC1)
(FRC2)
(FRC3)
After writing these data, synchronization can be checked by reading the three free-running
counters at the same interval as the write interval. If the read data have the same relative
differences as the write data, the three free-running timers are synchronized.
Programs for synchronizing the timers are shown next. Examples a, b, and c can be used when the
program is stored in on-chip memory. Examples d, e, and f can be used when the program is
stored in external memory. These programs assume that no wait states (T
W
) are inserted and there
is no NMI input.
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