PIC16F688

Manufacturer Part NumberPIC16F688
ManufacturerMicrochip Technology Inc.
PIC16F688 datasheet
 


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Page 47/202

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5.0
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
Figure 5-1 is a block diagram of the Timer0 module.
FIGURE 5-1:
BLOCK DIAGRAM OF THE TIMER0/WDT PRESCALER
F
/4
OSC
0
1
T0CKI
pin
0
T0CS
T0SE
1
PSA
WDTE
SWDTEN
Prescaler
31 kHz
Watchdog
INTOSC
Timer
Note 1:
T0SE, T0CS, PSA, PS<2:0> are bits in the OPTION register.
2:
SWDTEN and WDTPS<3:0> are bits in the WDTCON register.
3:
WDTE bit is in the Configuration Word register.
© 2007 Microchip Technology Inc.
5.1
Timer0 Operation
When used as a timer, the Timer0 module can be used
as either an 8-bit timer or an 8-bit counter.
5.1.1
8-BIT TIMER MODE
When used as a timer, the Timer0 module will
increment every instruction cycle (without prescaler).
Timer mode is selected by clearing the T0CS bit of the
OPTION register to ‘0’.
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.
5.1.2
8-BIT COUNTER MODE
When used as a counter, the Timer0 module will
increment on every rising or falling edge of the T0CKI
pin. The incrementing edge is determined by the T0SE
bit of the OPTION register. Counter mode is selected by
setting the T0CS bit of the OPTION register to ‘1’.
8-bit
Prescaler
PSA
8
PS<2:0>
16-bit
16
PSA
WDTPS<3:0>
PIC16F688
Data Bus
8
1
Sync
TMR0
2 Tcy
0
Set Flag bit T0IF
on Overflow
1
WDT
Time-out
0
DS41203D-page 45