PIC16C926 Microchip Technology Inc., PIC16C926 Datasheet - Page 47

• Manufacturer Part Number: PIC16C926
• Description: 64/68-pin Cmos Microcontrollers With Lcd Driver
• Manufacturer: Microchip Technology Inc.

5.3.1
The prescaler assignment is fully under software con-
trol, i.e., it can be changed “on the fly” during program
execution.
EXAMPLE 5-1:
To change prescaler from the WDT to the Timer0 mod-
ule use the precaution shown in Example 5-2.
EXAMPLE 5-2:
TABLE 5-1:
Lines 2 and 3 do NOT have to
be included if the final desired
prescale value is other than 1:1.
If 1:1 is final desired value, then
a temporary prescale value is
set in lines 2 and 3 and the final
prescale value will be set in lines
10 and 11.
01h, 101h
0Bh, 8Bh,
10Bh, 18Bh
81h, 181h
85h
Legend: x = unknown, u = unchanged, - = unimplemented locations read as '0'.
Address
2001 Microchip Technology Inc.
CLRWDT
BSF
MOVLW
MOVWF
BCF
Shaded cells are not used by Timer0.
STATUS, RP0
b’xxxx0xxx’
OPTION_REG
STATUS, RP0
SWITCHING PRESCALER
ASSIGNMENT
TMR0
INTCON
TRISA
OPTION RBPU INTEDG
Name
REGISTERS ASSOCIATED WITH TIMER0
CHANGING PRESCALER (TIMER0 WDT)
CHANGING PRESCALER (WDT TIMER0)
Timer0 Module Register
Bit 7
GIE
—
;Clear WDT and precaler
;Select Bank1
;Select TMR0,
;new prescale value and
;clock source
;Select Bank0
PEIE
Bit 6
1)
2)
3)
4)
5)
6)
7)
8)
9)
10) MOVLW
11) MOVWF
12) BCF
—
BSF
MOVLW
MOVWF
BCF
CLRF
BSF
MOVLW
MOVWF
CLRWDT
PORTA Data Direction Control Register
TMR0IE
T0CS
Bit 5
STATUS, RP0
b’xx0x0xxx’
OPTION_REG
STATUS, RP0
TMR0
STATUS, RP1
b’xxxx1xxx’
OPTION_REG
b’xxxx1xxx’
OPTION_REG
STATUS, RP0
Preliminary
T0SE
Bit 4
INTE
Bit 3
RBIE TMR0IF
PSA
;Select Bank1
;Select clock source and prescale value of
;other than 1:1
;Select Bank0
;Clear TMR0 and prescaler
;Select Bank1
;Select WDT, do not change prescale value
;
;Clears WDT and prescaler
;Select new prescale value and WDT
;
;Select Bank0
Note:
Bit 2
PS2
To avoid an unintended device RESET,
the following instruction sequence (shown
in Example 5-1) must be executed when
changing the prescaler assignment from
Timer0 to the WDT. This precaution must
be followed even if the WDT is disabled.
PIC16C925/926
Bit 1
INTF
PS1
Bit 0
RBIF
PS0
xxxx xxxx uuuu uuuu
0000 000x 0000 000u
1111 1111 1111 1111
--11 1111 --11 1111
Power-on
Value on
Reset
DS39544A-page 45
Value on
RESETS
all other