M16C29 Datasheet, PDF (131/499 Pages) Renesas Technology Corp – RENESAS MCU M16C FAMILY / M16C/Tiny SERIES

M16C/29 Group
12. Timer A
12.1.2 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 12.2 lists specifica-
tions in event counter mode (when not processing two-phase pulse signal). Table 12.3 lists specifica-
tions in event counter mode (when processing two-phase pulse signal with the timers A2, A3 and A4).
Figure 12.8 shows TAiMR register in event counter mode (when not processing two-phase pulse signal).
Figure 12.9 shows TA2MR to TA4MR registers in event counter mode (when processing two-phase
pulse signal with the timers A2, A3 and A4).
Table 12.2 Specifications in Event Counter Mode (when not processing two-phase pulse signal)
Item
Specification
Count source
• 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
Count operation
• Increment or decrement 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
Divided ratio
timer continues counting without reloading.
1/ (FFFF16 - n + 1) for increment
1/ (n + 1) for down-count n : set value of TAi register 000016 to FFFF16
Count start condition
Set TAiS bit in the TABSR register to 1 (start counting)
Count stop condition
Set TAiS bit to 0 (stop counting)
Interrupt request generation timing Timer overflow or underflow
TAiIN pin function
I/O port or count source input
TAiOUT pin function
I/O port, pulse output, or up/down-count select input
Read from timer
Count value can be read by reading TAi register
Write to timer
• 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)
Select function
• 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 not counting, the pin outputs a low.
Rev. 1.12 Mar.30, 2007 ^{page 107} of 458
REJ09B0101-0112