PIC16C63A Microchip Technology, PIC16C63A Datasheet - Page 38

• Manufacturer Part Number: PIC16C63A
• Description: 28/40-Pin 8-Bit CMOS Microcontrollers
• Manufacturer: Microchip Technology

PIC16C63A/65B/73B/74B
4.2.1
The prescaler assignment is fully under software con-
trol, i.e., it can be changed “on the fly” during program
execution.
FIGURE 4-2:
TABLE 4-1:
DS30605A-page 38
Address
01h
0Bh, 8Bh
81h
85h
Legend: x = unknown, u = unchanged, - = unimplemented locations read as '0'. Shaded cells are not used by Timer0.
Note:
RA4/T0CKI
CLKOUT (=Fosc/4)
WDT Enable bit
Watchdog
Note: T0CS, T0SE, PSA, PS2:PS0 are (OPTION_REG<5:0>).
pin
Timer
SWITCHING PRESCALER ASSIGNMENT
To avoid an unintended device RESET, a
specific instruction sequence (shown in the
PICmicro
(DS33023). must be executed when
changing the prescaler assignment from
Timer0 to the WDT. This sequence must be
followed even if the WDT is disabled.
Name
TMR0
INTCON
OPTION_REG
TRISA
BLOCK DIAGRAM OF THE TIMER0/WDT PRESCALER
REGISTERS ASSOCIATED WITH TIMER0
T0SE
Mid-Range Reference Manual,
0
1
Timer0 module’s register
RBPU INTEDG T0CS
Bit 7
GIE
PSA
—
M
U
X
0
1
Bit 6
PEIE
T0CS
—
M
U
X
PORTA Data Direction Register
Bit 5
T0IE
0
8-bit Prescaler
8 - to - 1MUX
Time-out
8
M U X
WDT
T0SE
INTE
Bit 4
1
0
1
PSA
M
U
X
RBIE
Bit 3
PSA
4.3
The TMR0 interrupt is generated when the TMR0 reg-
ister overflows from FFh to 00h. This overflow sets bit
T0IF (INTCON<2>). The interrupt can be masked by
clearing bit T0IE (INTCON<5>). Bit T0IF must be
cleared in software by the Timer0 module interrupt ser-
vice routine before re-enabling this interrupt. The TMR0
interrupt cannot awaken the processor from SLEEP
since the timer is shut off during SLEEP.
PSA
Bit 2
T0IF
PS2
PS2:PS0
Timer0 Interrupt
Cycles
SYNC
2
Bit 1
INTF
PS1
Bit 0
RBIF
PS0
1998 Microchip Technology Inc.
TMR0 reg
Data Bus
xxxx xxxx
0000 000x
1111 1111
--11 1111
Value on
POR,
BOR
8
Set flag bit T0IF
on Overflow
other resets
Value on all
uuuu uuuu
0000 000u
1111 1111
--11 1111