M16C6S_09 Datasheet, PDF (83/208 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

M16C/6S Group
Timer A
2. Event Counter Mode
In event counter mode, the timer counts pulses from an external device or overflows and underflows of
other timers. Timer A4 can count two-phase external signals. Table 1.12.2 lists specifications in event
counter mode (when not processing two-phase pulse signal). Table 1.12.3 lists specifications in event
counter mode (when processing two-phase pulse signal with the timer A4). Figure 1.12.7 shows TAiMR
register in event counter mode (when not processing two-phase pulse signal). Figure 1.12.8 shows
TA4MR registers in event counter mode (when processing two-phase pulse signal with the timer A4).
Table 1.12.2. 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 Aj (j=i-1, except j=4 if i=0) overflows or underflows,
Count operation
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.
Divided ratio
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 of 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
TAiOUT pin function
I/O port or count source input
i≠2, 3
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.5.01 Dec 10, 2009 page 83 of 201
REJ03B0014-0501