Datasheet

PIC16C62X
DS30235J-page 34  2003 Microchip Technology Inc.
6.3 Prescaler
An 8-bit counter is available as a prescaler for the
Timer0 module, or as a postscaler for the Watchdog
Timer, respectively (Figure 6-6). For simplicity, this
counter is being referred to as “prescaler” throughout
this data sheet. Note that there is only one prescaler
available which is mutually exclusive between the
Timer0 module and the Watchdog Timer. Thus, a
prescaler assignment for the Timer0 module means
that there is no prescaler for the Watchdog Timer and
vice-versa.
The PSA and PS<2:0> 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 1,
MOVWF 1, BSF 1,x....etc.) will clear the prescaler.
When assigned to WDT, a CLRWDT instruction will clear
the prescaler along with the Watchdog Timer. The
prescaler is not readable or writable.
FIGURE 6-6: BLOCK DIAGRAM OF THE TIMER0/WDT PRESCALER
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
PS<2:0>
8
Note: T0SE, T0CS, PSA, PS<2:0> are bits in the OPTION register.
PSA
WDT Enable bit
M
U
X
0
1
0
1
Data Bus
Set flag bit T0IF
on Overflow
8
PSA
T0CS