R8C/20 Group, R8C/21 Group 14. Timers
Rev.2.00 Aug 27, 2008 Page 150 of 458
REJ09B0250-0200
14.2.3.1 One-Shot Trigger Selection
In programmable one-shot generation mode and programmable wait one-shot generation mode, operation starts
when a one-shot trigger is generated while the TCSTF bit in the TRBCR register is set to 1 (count starts).
A one-shot trigger can be generated by either of the following causes:
• 1 is written to the TOSST bit in the TRBOCR register by a program.
• Trigger input from the INT0 pin.
When a one-shot trigger occurs, the TOSSTF bit in the TRBOCR register is set to 1 (one-shot operation in
progress) after one or two cycles of the count source have elapsed. Then, in programmable one-shot generation
mode, count operation begins and one-shot waveform output starts. (In programmable wait one-shot generation
mode, count operation starts for the wait period.) If a one-shot trigger occurs while the TOSSTF bit is set to 1,
no retriggering occurs.
To use trigger input from the INT0
pin, input the trigger after making the following settings:
• Set the PD4_5 bit in the PD4 register to 0 (input port).
• Select the INT0 digital filter with bits INT0F1 and INT0F0 in the INTF register.
• Select both edges or one edge with the INT0PL bit in INTEN register. If one edge is selected, further select
falling or rising edge with the INOSEG bit in TRBIOC register.
• Set the INT0EN bit in the INTEN register to 0 (enabled).
• After completing the above, set the INOSTG bit in the TRBIOC register to 1 (INT pin one-shot trigger
enabled).
Note the following points with regard to generating interrupt requests by trigger input from the INT0
pin.
• Processing to handle the interrupts is required. Refer to 12. Interrupts for details.
• If one edge is selected, use the POL bit in the INT0IC register to select falling or rising edge. (The
INOSEG bit in the TRBIOC register does not affect INT0
interrupts).
• If a one-shot trigger occurs while the TOSSTF bit is set to 1, timer RB operation is not affected, but the
value of the IR bit in the INT0IC register changes.
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