EM88F758N datasheet(91/190 Pages) EMC

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EM88F758N

8-Bit Microcontroller

Product Specification (V1.1) 03.25.2016

 81

(This specification is subject to change without prior notice)

6.2

TCC/WDT and Prescaler

There are two 8-bit counters available as prescalers for the TCC and WDT respectively.

The TPSR0~ TPSR2 bits of the TCCCR register are used to determine the ratio of the

prescaler of TCC. Likewise, the WPSR0~WPSR2 bits of the WDTCR register are used

to determine the prescaler of WDT. The prescaler counter will be cleared by the

instructions each time they are written into TCC. The WDT and prescaler will be

cleared by the “WDTC” and “SLEP” instructions. Figure 6-4 depicts the circuit diagram

of TCC/WDT.

TCCD is an 8-bit timer/counter. The clock source of TCC can be internal clock or

external signal input (edge selectable from the TCC pin). If TCC signal source is from

internal clock, TCC will increase by 1 at every instruction cycle (without prescaler). If

TCC signal source is from external clock input, TCC will increase by 1 at every falling

edge or rising edge of the TCC pin. TCC pin input time length (keep in High or low level)

must greater than 1CLK.

If TCC signal source is from internal clock, the TCC will stop running when sleep

mode occurs.

If TCC signal source is from external clock, TCC will increase by 1 at every

falling edge or rising edge of the TCC pin when sleep mode occurs.

The watchdog timer is a free running on-chip RC oscillator. The WDT will keep on

running even after the oscillator driver has been turned off (i.e. in sleep mode). During

the normal operation or the sleep mode, a WDT time-out (if enabled) will cause the

device to reset. The WDT can be enabled or disabled at any time during the normal

mode by software programming. Refer to WDTE bit of WDTCR register. With no

prescaler, the WDT time-out period is approximately 16.5 ms

1 (one oscillator start-up

timer period).

1 Note: VDD=5V, WDT time-out period = 16.5ms ± 5%.

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