M16C26A Datasheet, PDF (115/352 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/Tiny SERIES

M16C/26A Group (M16C/26A, M16C/26B, M16C/26T)
12. Timer
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 12.1.2.1 lists specifica-
tions in event counter mode (when not processing two-phase pulse signal). Table 12.1.2.2 lists specifica-
tions in event counter mode (when processing two-phase pulse signal with the timers A2, A3 and A4).
Figure 12.1.2.1 shows TAiMR register in event counter mode (when not processing two-phase pulse
signal). Figure 12.1.2.2 shows TA2MR to TA4MR registers in event counter mode (when processing two-
phase pulse signal with the timers A2, A3 and A4).
Table 12.1.2.1. 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
• 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
Divided ratio
timer continues counting without reloading.
1/ (FFFF16 - n + 1) for up-count
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. 2.00 Feb.15, 2007 ^{page 98} of 329
REJ09B0202-0200