Microchip Technology PIC16F716, Datasheet

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PIC16F716
DS41206A-page 28
Preliminary

2003 Microchip Technology Inc.
4.2.1 SWITCHING PRESCALER
ASSIGNMENT
The prescaler assignment is fully under software
control (i.e., it can be changed “on-the-fly” during
program execution).
4.3 Timer0 Interrupt
The TMR0 interrupt is generated when the TMR0
register 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
service routine before re-enabling this interrupt. The
TMR0 interrupt cannot awaken the processor from
Sleep since the timer is shut off during Sleep.
FIGURE 4-2: BLOCK DIAGRAM OF THE TIMER0/WDT PRESCALER
TABLE 4-1: REGISTERS ASSOCIATED WITH TIMER0
Note: To avoid an unintended device Reset, a
specific instruction sequence (shown in
the PICmicro
®
Mid-Range Reference
Manual, 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.
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Value on:
POR,
BOR
Value on all
other Resets
01h TMR0 Timer0 module’s register
xxxx xxxx uuuu uuuu
0Bh,8Bh INTCON GIE PEIE T0IE INTE RBIE T0IF INTF RBIF
0000 000x 0000 000u
81h OPTION_REG RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0
1111 1111 1111 1111
85h TRISA — — —
(1)
Bit 4 PORTA Data Direction Register
--11 1111 --11 1111
Legend:
x
= unknown,
u
= unchanged,
-
= unimplemented locations read as ‘
0
’. Shaded cells are not used by Timer0
.
Note 1: Reserved bits, do not use.
RA4/T0CKI
T0SE
pin
M
U
X
CLKOUT (=F
OSC
/4)
SYNC
2
Cycles
TMR0 reg
8-bit Prescaler
8 - to - 1MUX
M
U
X
M U X
Watchdog
Timer
PSA
0
1
0
1
WDT
Time-out
PS2:PS0
8
PSA
WDT Enable bit
M
U
X
0
1
0
1
Data Bus
Set flag bit T0IF
on Overflow
8
PSA
T0CS
Note:
T0CS, T0SE, PSA, PS2:PS0 are (OPTION_REG<5:0>).