PIC16F720_13 Datasheet, PDF (89/254 Pages) Microchip Technology – 20-Pin Flash Microcontrollers

PIC16(L)F720/721
12.0 TIMER0 MODULE
The Timer0 module is an 8-bit timer/counter with the
following features:
• 8-bit timer/counter register (TMR0)
• 8-bit prescaler (shared with Watchdog Timer)
• Programmable internal or external clock source
• Programmable external clock edge selection
• Interrupt on overflow
• TMR0 can be used to gate Timer1
Figure 12-1 is a block diagram of the Timer0 module.
12.1 Timer0 Operation
The Timer0 module can be used as either an 8-bit timer
or an 8-bit counter.
12.1.1 8-BIT TIMER MODE
The Timer0 module will increment every instruction
cycle, if used without a prescaler. 8-Bit Timer mode is
selected by clearing the T0CS bit of the OPTION_REG
register.
When TMR0 is written, the increment is inhibited for
two instruction cycles immediately following the write.
Note:
The value written to the TMR0 register
can be adjusted, in order to account for
the two instruction cycle delay when
TMR0 is written.
12.1.2 8-BIT COUNTER MODE
In 8-Bit Counter mode, the Timer0 module will increment
on every rising or falling edge of the T0CKI pin.
8-Bit Counter mode using the T0CKI pin is selected by
setting the T0CS bit in the OPTION_REG register to ‘1’.
The rising or falling transition of the incrementing edge
for either input source is determined by the T0SE bit in
the OPTION_REG register.
FIGURE 12-1:
BLOCK DIAGRAM OF THE TIMER0/WDT PRESCALER
FOSC/4
T0CKI
T1GSS = 11
TMR1GE
WDTEN
0
1
0
T0SE
T0CS
1
PSA
8-bit
Prescaler
8
1
SYNC
2 TCY
0
PSA
Data Bus
8
TMR0
Set Flag bit T0IF
on Overflow
Overflow to Timer1
Low-Power
WDT
Divide by
512
PS<2:0>
1
WDT
Time-out
0
PSA
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DS41430D-page 89