PIC16C641-04SLASHSP datasheet(44/136 Pages) MICROCHIP

44 / 136 page

PIC16C64X & PIC16C66X

DS30559A-page 44

Preliminary

6.3

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 6-6). 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.

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 1, MOVWF 1,

BSF

1,x

) will clear the prescaler count. When

assigned to Watchdog Timer, a CLRWDT instruction will

clear the prescaler count along with the Watchdog

Timer. The prescaler is not readable or writable.

FIGURE 6-6:

BLOCK DIAGRAM OF THE TIMER0/WDT PRESCALER

RA4/T0CKI

T0SE

CLKOUT (=Fosc/4)

SYNC

Cycles

TMR0 reg

8-bit Prescaler

8 - to - 1MUX

M U X

Watchdog

Timer

PSA

WDT

Time-out

PS2:PS0

Note: T0CS, T0SE, PSA, PS2:PS0 are (OPTION<5:0>).

PSA

WDT Enable bit

Data Bus

Set ﬂag bit T0IF

on Overﬂow

PSA

T0CS

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