PIC16F628-20/P Microchip Technology Inc., PIC16F628-20/P Datasheet - Page 47

• Manufacturer Part Number: PIC16F628-20/P
• Description: 18 PIN, 3.5 KB FLASH, 224 RAM, 16 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F628-20/P

• Comparators: 2
• Cpu Speed: 5 MIPS
• Eeprom Memory: 128 Bytes
• Input Output: 16
• Interface: SCI/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 18-pin PDIP
• Programmable Memory: 3.5K Bytes
• Ram Size: 224 Bytes
• Speed: 20 MHz
• Timers: 2-8-bit, 1-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

6.3.1
The prescaler assignment is fully under software
control (i.e., it can be changed “on the fly” during
program execution). Use the instruction sequences,
shown in Example 6-1, when changing the prescaler
assignment from Timer0 to WDT, to avoid an
unintended device RESET.
EXAMPLE 6-1:
TABLE 6-1:
 2003 Microchip Technology Inc.
01h
0Bh/8Bh/
10Bh/18Bh
81h, 181h
85h
Legend:
Note 1: Shaded bits are not used by TMR0 module.
Address
BCF
CLRWDT
CLRF
BSF
MOVLW
MOVWF
CLRWDT
MOVLW
MOVWF
BCF
2: Option is referred by OPTION_REG in MPLAB.
— = Unimplemented locations, read as ‘0’, u = unchanged, x = unknown
SWITCHING PRESCALER
ASSIGNMENT
TMR0
INTCON
OPTION
TRISA
STATUS, RP0
TMR0
STATUS, RP0
'00101111’b
OPTION_REG
'00101xxx’b
OPTION_REG
STATUS, RP0
Name
REGISTERS ASSOCIATED WITH TIMER0
(2)
CHANGING PRESCALER
(TIMER0→WDT)
Timer0 module register
TRISA7
RBPU
Bit 7
GIE
;Skip if already in
;Bank 0
;Clear WDT
;Clear TMR0 & Prescaler
;Bank 1
;These 3 lines
;(5, 6, 7)
;are required only
;if desired PS<2:0>
;are
;000 or 001
;Set Postscaler to
;desired WDT rate
;Return to Bank 0
INTEDG
TRISA6 TRISA5 TRISA4 TRISA3 TRISA2 TRISA1 TRISA0 1111 1111 1111 1111
Bit 6
PEIE
T0CS
Bit 5
T0IE
Preliminary
T0SE
Bit 4
INTE
Bit 3
RBIE
PSA
To change prescaler from the WDT to the TMR0
module use the sequence shown in Example 6-2. This
precaution must be taken even if the WDT is disabled.
EXAMPLE 6-2:
CLRWDT
BSF
MOVLW
MOVWF
BCF
Bit 2
T0IF
PS2
STATUS, RP0
b'xxxx0xxx' ;Select TMR0, new
OPTION_REG
STATUS, RP0
Bit 1
INTF
PS1
CHANGING PRESCALER
(WDT→TIMER0)
Bit 0
RBIF
PS0
PIC16F62X
;Clear WDT and
;prescaler
;prescale value and
;clock source
xxxx xxxx uuuu uuuu
0000 000x 0000 000u
1111 1111 1111 1111
Value on
POR
DS40300C-page 45
All Other
Value on
RESETS