Datasheet

PIC16C6X
DS30234E-page 68  1997-2013 Microchip Technology Inc.
7.3 Prescaler
An 8-bit counter is available as a prescaler for the
Timer0 module or as a postscaler for the Watchdog
Timer (WDT), respectively (Figure 7-6). For simplicity,
this counter is being referred to as “prescaler” through-
out this data sheet. Note that the prescaler may be
used by either the Timer0 module or the Watchdog
Timer, but not both. Thus, a prescaler assignment for
the Timer0 module means that there is no prescaler for
the Watchdog Timer, and vice-versa.
Applicable Devices
61 62 62A R62 63 R63 64 64A R64 65 65A R65 66 67
The PSA and PS2:PS0 bits (OPTION<3:0>) determine
the prescaler assignment and prescale ratio.
When assigned to the Timer0 module, all instructions
writing to the TMR0 register (e.g. CLRF TMR0,
MOVWF TMR0, BSF TMR0,bitx) will clear the pres-
caler count. When assigned to the Watchdog Timer, a
CLRWDT instruction will clear the Watchdog Timer and
the prescaler count. The prescaler is not readable or
writable.
Note: Writing to TMR0 when the prescaler is
assigned to Timer0 will clear the prescaler
count, but will not change the prescaler
assignment.
FIGURE 7-6: BLOCK DIAGRAM OF THE TIMER0/WDT PRESCALER
RA4/T0CKI
T0SE
pin
M
U
X
CLKOUT (=Fosc/4)
SYNC
2
Cycles
TMR0 reg
8-bit Prescaler
8 - to - 1MUX
M
U
X
M U X
Watchdog
Timer
PSA
0
1
0
1
WDT
Time-out
PS2:PS0
8
Note: T0CS, T0SE, PSA, PS2:PS0 are (OPTION<5:0>).
PSA
WDT Enable bit
M
U
X
0
1
0
1
Data Bus
Set flag bit T0IF
on Overflow
8
PSA
T0CS