
Rev.2.10 Apr 14, 2006 page 352 of 378
REJ09B0124-0210
M16C/6N Group (M16C/6NK, M16C/6NM) 23. Usage Notes
23.10.1.3 Timer A (One-shot Timer Mode)
The timer remains idle after reset. Set the mode, count source, counter value, etc. using the TAiMR
(i = 0 to 4) register, the TAi register, bits TA0TGL and TA0TGH in the ONSF register, and the TRGSR
register before setting the TAiS bit in the TABSR register to 1 (count starts).
Always make sure the TAiMR register, bits TA0TGL and TA0TGH, and the TRGSR register are modified
while the TAiS bit remains 0 (count stops) regardless whether after reset or not.
When setting the TAiS bit to 0 (count stops), the followings occur:
• A counter stops counting and a content of reload register is reloaded.
• TAiOUT pin outputs “L”.
• After one cycle of the CPU clock, the IR bit in the TAiIC register is set to 1 (interrupt request).
Output in one-shot timer mode synchronizes with a count source internally generated. When an external
trigger has been selected, one-cycle delay of a count source as maximum occurs between a trigger
input to TAiIN pin and output in one-shot timer mode.
The IR bit is set to 1 when timer operating mode is set with any of the following procedures:
• Select one-shot timer mode after reset.
• Change an operating mode from timer mode to one-shot timer mode.
• Change an operating mode from event counter mode to one-shot timer mode.
To use the timer Ai interrupt (the IR bit), set the IR bit to 0 after the changes listed above have been
made.
When a trigger occurs, while counting, a counter reloads the reload register to continue counting after
generating a re-trigger and counting down once. To generate a trigger while counting, generate a second
trigger between occurring the previous trigger and operating longer than one cycle of a timer count
source.
When the external trigger is selected as count start condition, do not input again the external trigger
between 300 ns before the counter reaches 0000h.
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If a low-level signal is applied to the NMI pin when the IVPCR1 bit in the TB2SC register = 1 (three-phase
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output forcible cutoff by input on NMI pin enabled), pins TA1OUT, TA2OUT, and TA4OUT go to a
high-impedance state.
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