PIC16F720-ESLASHML datasheet(98/244 Pages) MICROCHIP

98 / 244 page

PIC16F/LF720/721

DS41430A-page 98

 2010 Microchip Technology Inc.

13.5.2.1

T1G Pin Gate Operation

The T1G pin is one source for Timer1 gate control. It

can be used to supply an external source to the Timer1

gate circuitry.

13.5.2.2

Timer0 Overflow Gate Operation

When Timer0 increments from FFh to 00h, a low-to-

high pulse will automatically be generated and

internally supplied to the Timer1 gate circuitry.

13.5.2.3

Timer2 Match Gate Operation

The TMR2 register will increment until it matches the

value in the PR2 register. On the very next increment

cycle, TMR2 will be reset to 00h. When this Reset

occurs, a low-to-high pulse will automatically be

generated and internally supplied to the Timer1 gate

circuitry.

13.5.2.4

Watchdog Overflow Gate Operation

The Watchdog Timer oscillator, prescaler and counter

will be automatically turned on when TMR1GE = 1 and

T1GSS selects the WDT as a gate source for Timer1

(T1GSS = 11). TMR1ON does not factor into the oscil-

lator, prescaler and counter enable. See Table 13-5.

The PSA and PS bits of the OPTION register still

control what time-out interval is selected. Changing the

prescaler during operation may result in a spurious

capture.

Enabling the Watchdog Timer oscillator does not

automatically enable a Watchdog Reset or Wake-up

from Sleep upon counter overflow.

As the gate signal coming from the WDT counter will

generate different pulse widths depending on if the

WDT is enabled, when the CLRWDT instruction is

executed, and so on, Toggle mode must be used. A

specific sequence is required to put the device into the

correct state to capture the next WDT counter interval.

Note:

When using the WDT as a gate source for

Timer1, operations that clear the Watchdog

Timer (CLRWDT, SLEEP instructions) will

affect the time interval being measured.

This includes waking from Sleep. All other

interrupts that might wake the device from

Sleep should be disabled to prevent them

from disturbing the measurement period.

TABLE 13-5:

WDT/TIMER1 GATE INTERACTION

WDTE

TMR1GE = 1

and

T1GSS = 11

WDT Oscillator

Enable

WDT Reset

Wake-up

WDT Available for

T1G Source

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