M16C User Manual.pdf

Timer AMitsubishi microcomputersM16C / 62 GroupSINGLE-CHIP 16-BIT CMOS MICROCOMPUTER2.2.15 Precautions for Timer A (one-shot timer mode)(1) At reset, the count start flag is set to “0”. Set a value in the timer Ai register, then set the flagto “1”.(2) Setting the count start flag to “0” while a count is in progress causes as follows:• The counter stops counting and a content of reload register is reloaded.• The TAiOUT pin outputs “L” level.• The interrupt request generated and the timer Ai interrupt request bit goes to “1”.(3) The output from the one-shot timer synchronizes with the count source generated internally.Therefore, when an external trigger has been selected, a delay of one cycle of count sourceas a maximum occurs between the trigger input to the TAiIN pin and the one-shot timeroutput.(4) The timer Ai interrupt request bit goes to “1” if the timer's operation mode is set using any ofthe following procedures:• Selecting one-shot timer mode after reset.• Changing operation mode from timer mode to one-shot timer mode.• Changing operation mode from event counter mode to one-shot timer mode.Therefore, to use timer Ai interrupt (interrupt request bit), set timer Ai interrupt request bit to“0” after the above listed changes have been made.(5) If a trigger occurs while a count is in progress, after the counter performs one down countfollowing the reoccurrence of a trigger, the reload register contents are reloaded, and thecount continues. To generate a trigger while a count is in progress, generate the secondtrigger after an elapse longer than one cycle of the timer's count source after the previoustrigger occurred.TAiIN pin input signal“H”“L”Trigger inputCount sourceOne-shot pulseoutput from TAiOUT pinStart one-shot pulse outputNote: The above applies when an external trigger (falling edge of TAiIN pin input signal) is selected.Figure 2.2.31. One-shot timer delay310