PIC12C67X Datasheet, PDF (43/129 Pages) Microchip Technology – 8-Pin, 8-Bit CMOS Microcontroller with A/D Converter and EEPROM Data Memory

PIC12C67X
7.3.1 SWITCHING PRESCALER ASSIGNMENT
The prescaler assignment is fully under software con-
trol, (i.e., it can be changed “on-the-fly” during program
execution).
Note:
To avoid an unintended device RESET, the
following instruction sequence (shown in
Example 7-1) must be executed when
changing the prescaler assignment from
Timer0 to the WDT. This sequence must
be followed even if the WDT is disabled.
EXAMPLE 7-1: CHANGING PRESCALER
(TIMER0→WDT)
BCF STATUS, RP0
CLRF TMR0
BSF STATUS, RP0
CLRWDT
MOVLW b’xxxx1xxx’
MOVWF OPTION_REG
BCF STATUS, RP0
;Bank 0
;Clear TMR0 & Prescaler
;Bank 1
;Clears WDT
;Select new prescale
;value & WDT
;Bank 0
To change prescaler from the WDT to the Timer0 mod-
ule, use the sequence shown in Example 7-2.
EXAMPLE 7-2: CHANGING PRESCALER
(WDT→TIMER0)
CLRWDT
BSF
MOVLW
MOVWF
BCF
;Clear WDT and
;prescaler
STATUS, RP0 ;Bank 1
b’xxxx0xxx’ ;Select TMR0, new
;prescale value and
OPTION_REG ;clock source
STATUS, RP0 ;Bank 0
TABLE 7-1: REGISTERS ASSOCIATED WITH TIMER0
Address Name Bit 7 Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR
Value on
all other
Resets
01h
TMR0 Timer0 module’s register
xxxx xxxx uuuu uuuu
0Bh/8Bh INTCON GIE PEIE
T0IE
INTE GPIE T0IF INTF GPIF 0000 000x 0000 000u
81h
OPTION GPPU INTEDG T0CS T0SE PSA PS2 PS1 PS0 1111 1111 1111 1111
85h
TRIS
—
—
TRIS5 TRIS4 TRIS3 TRIS2 TRIS1 TRIS0 --11 1111 --11 1111
Legend: x = unknown, u = unchanged, - = unimplemented locations read as '0'. Shaded cells are not used by Timer0.
© 1999 Microchip Technology Inc.
DS30561B-page 43