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M16C/26 Group
Rev.0.90 2003.12.28 page 10 of 28
Under development
Preliminary specification
Specifications in this manual are tentative and subject to change.
1.5.1.3 Timer A (One-shot Timer Mode)
1. 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, the ONSF register TA0TGL and TA0TGH bits and the TRGSR
register before setting the TAiS bit in the TABSR register to “1” (count starts).
Always make sure the TAiMR register, the ONSF register TA0TGL and TA0TGH bits and the
TRGSR register are modified while the TAiS bit remains “0” (count stops) regardless whether after
reset or not.
2. When setting TAiS bit to “0” (count stop), 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 of TAiIC register is set to “1” (interrupt request).
3. 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.
4. The IR bit is set to “1” when timer operation mode is set with any of the following procedures:
• Select one-shot timer mode after reset.
• Change an operation mode from timer mode to one-shot timer mode.
• Change an operation 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.
5. 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, gener-
ate a second trigger between occurring the previous trigger and operating longer than one cycle of
a timer count source.
_______ _____
6. If a low-level signal is applied to the P85/NMI/SD pin when the TB2SC register IVPCR1 bit = “1”
_____
(three-phase output forcible cutoff by input on SD pin enabled), the TA1OUT, TA2OUT and TA4OUT
pins go to a high-impedance state.
1.5 Precautions for Timers