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M16C/62P Group (M16C/62P, M16C/62PT)
15.1.2 Event Counter Mode
In event counter mode, the timer counts pulses from an external device or overflows and underflows of
other timers. Timers A2, A3 and A4 can count two-phase external signals. Table 15.2 lists specifications
in event counter mode (when not processing two-phase pulse signal). Table 15.3 lists specifications in
event counter mode (when processing two-phase pulse signal with Timers A2, A3 and A4). Figure 15.8
shows TAiMR register in event counter mode (when not processing two-phase pulse signal). Figure 15.9
shows TA2MR to TA4MR registers in event counter mode (when processing two-phase pulse signal with
Timers A2, A3 and A4).
Table 15.2. Specifications in Event Counter Mode (when not processing two-phase pulse signal)
Item
Count Source
Count Operation
Divided Ratio
Count Start Condition
Count Stop Condition
Interrupt Request Generation Timing
TAiIN Pin Function
TAiOUT Pin Function
Read from Timer
Write to Timer
Select Function
R
e
. v
2
3 .
0
S
e
p
0
, 1
2
0
0
4
R
E
J
0
9
B
0
1
8
5
0 -
2
3
0
Z
• External signals input to TAiIN pin (i=0 to 4) (effective edge can be
selected in program)
• Timer B2 overflows or underflows,
Timer Aj (j=i-1, except j=4 if i=0) overflows or underflows,
Timer Ak (k=i+1, except k=0 if i=4) overflows or underflows
• Up-count or down-count can be selected by external signal or program
• When the timer overflows or underflows, it reloads the reload register
contents and continues counting. When operating in free-running mode,
the timer continues counting without reloading.
1/ (FFFFh - n + 1) for up-count
1/ (n + 1) for down-count
Set TAiS bit in the TABSR register to "1" (= start counting)
Set TAiS bit to "0" (= stop counting)
Timer overflow or underflow
I/O port or count source input
I/O port, pulse output, or up/down-count select input
Count value can be read by reading TAi register
• When not counting and until the 1st count source is input after counting start
Value written to TAi register is written to both reload register and counter
• When counting (after 1st count source input)
Value written to TAi register is written to only reload register
(Transferred to counter when reloaded next)
• Free-run count function
Even when the timer overflows or underflows, the reload register content
is not reloaded to it
• Pulse output function
Whenever the timer underflows or underflows, the output polarity of
TAiOUT pin is inverted. When TAiS bit is set to "0" (stop counting),
the pin outputs a low.
page 127
f o
3
6
4
Specification
n : set value of TAi register 0000h to FFFFh
15. Timers
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