E202075_HD404889 Datasheet, PDF (98/202 Pages) Renesas Technology Corp – Low-Voltage AS Microcomputers with On-Chip LCD Circuit

HD404889/HD404899/HD404878/HD404868 Series
Timer C Operation
• Free-running/reload timer:
Free-running/reload timer operation, the input clock source, and the prescaler division ratio are selected
by means of timer mode register C1 (TMC1).
Timer C is initialized to the value written to timer write register C (TWCL, TWCU) by software, and
counts up by 1 each time the input clock is input. When the input clock is input after the timer C value
reaches $FF, overflow output is generated. Timer C is then set to the value in timer write register C
(TWCL, TWCU) if the reload timer function is selected, or to $00 if the free-running timer function is
selected, and starts counting up again.
Overflow output sets the timer C interrupt request flag (IFTC). This flag is reset by the program or by
an MCU reset.
For details, see figure 3, Interrupt Control Bit and Register Flag Area Configuration, and table 1, Initial
Values after MCU Reset.
• 16-bit timer operation:
When timer B overflow flag is selected as the clock source, timer C can be used as a 16-bit timer that
counts the timer B clock source pulses. In this case, since the timer B and timer C free-running/reload
settings are independent, the settings should be made to suit the purpose.
• Watchdog timer operation:
By using the timer C overflow output, timer C can be used as a watchdog timer for detecting program
runaway. The watchdog timer is enabled when the watchdog on flag (WDON) is set to 1, and generates
an MCU reset when timer C overflows. Usually, timer C initialization is performed by the program
before the timer C value reaches $FF, so controlling program runaway.
• Timer output operation:
With timer C, the R2₀/TOC pin is designated as the TOC pin by setting bit 0 of port mode register 3
(PMR3) to 1, and toggle waveform output or PWM waveform output can be selected by timer mode
register C2 (TMC2).
 Toggle output
The operation is similar to that for timer B toggle output.
 PWM output
The operation is similar to that for timer B PWM output.
• Module standby:
The operation is similar to that for timer B module standby.
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