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CHAPTER 14 MULTI-FUNCTIONAL TIMER
■ Timer Mode
Two count modes can be selected in 16-bit free-run timer
• up-count mode (TCCSL:MODE=0)
• up-down count mode (TCCSL:MODE=1)
In up-count mode, counter starts counting from pre-set timer data register (TCDT), counts up until counter
value matches value of compare clear register (CPCLR), then counter is cleared to "0000
up again.
In up-down count mode, counter starts counting from pre-set timer data register (TCDT), counts up until
counter value matches value of compare clear register (CPCLR), then counter changes from up-count to
down-count, counts down until counter value reaches "0000
There is a buffer in mode bit, TCCSL:MODE, it can be written at any time no matter the timer is operating
or stopped. While the timer is operating, value written to this bit is buffered and the count mode will be
changed when timer value is "0000
Counter value
FFFF
BFFF
7FFF
3FFF
0000
Reset
Compare clear
buffer register
TCCSL:MODE
326
H
Figure 14.6-2 Change Timer Mode while Timer is Operating
H
H
H
H
H
Timer starts
Change to up-down mode
" and then counts up again.
H
".
Change to up mode
BFFF
H
" and then counts
H
Time
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