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M16C/6N Group (M16C/6NK, M16C/6NM)
13.1.2 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 13.2 lists specifications
in event counter mode (when not processing two-phase pulse signal). Figure 13.8 shows TAiMR register
in event counter mode (when not processing two-phase pulse signal). Table 13.3 lists specifications in
event counter mode (when processing two-phase pulse signal with the timers A2, A3 and A4). Figure
13.9 shows TA2MR to TA4MR registers in event counter mode (when processing two-phase pulse signal
with the timers A2, A3 and A4).
Table 13.2 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 Timer overflow or underflow
TAiIN Pin Function
TAiOUT Pin Function
Read from Timer
Write to Timer
Select Function
i = 0 to 4
j = i - 1, except j = 4 if i = 0
k = i + 1, except k = 0 if i = 4
Rev.2.00
Nov 28, 2005
REJ09B0124-0200
• External signals input to TAiIN pin (effective edge can be selected in program)
• Timer B2 overflows or underflows,
Timer Aj overflows or underflows,
Timer Ak 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 the TAiS bit in the TABSR register to "1" (start counting)
Set the TAiS bit to "0" (stop counting)
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 the TAi register
• When not counting and until the 1st count source is input after counting start
Value written to the TAi register is written to both reload register and counter
• When counting (after 1st count source input)
Value written to the 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 120 of 378
Specification
n : set value of the TAi register 0000h to FFFFh
13. Timers
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