Event Counter Mode - Renesas M16C/60 Series Hardware Manual

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M16C/6N5 Group

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 1.13.2 lists specifications
in event counter mode (when not processing two-phase pulse signal). Figure 1.13.8 shows TAiMR register
in event counter mode (when not processing two-phase pulse signal). Table 1.13.3 lists specifications in
event counter mode (when processing two-phase pulse signal with the timers A2, A3 and A4). Figure
1.13.9 shows TA2MR to TA4MR registers in event counter mode (when processing two-phase pulse
signal with the timers A2, A3 and A4).
Table 1.13.2 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
TAi pin function
IN
TAi pin function
OUT
Read from timer
Write to timer
Select function
i = 0 to 4
Rev.1.00 2003.05.30 page 104
• External signals input to TAi
gram)
• 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 con-
tents and continues counting. When operating in free-running mode, the
timer continues counting without reloading.
1/ (FFFF - n + 1) for up-count
16
1/ (n + 1) for down-count
Set TAiS bit of TABSR register to "1" (start counting)
Set 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 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 TAi
pin is inverted. When not counting, the pin outputs a low.
Specification
pin (effective edge can be selected in pro-
IN
n : set value of TAi register
Timer A
0000 to FFFF
16 16
OUT