
PIC17C4X
DS30412C-page 70
1996 Microchip Technology Inc.
FIGURE 11-5: TMR0 READ/WRITE IN TIMER MODE
TABLE 11-1:
REGISTERS/BITS ASSOCIATED WITH TIMER0
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
Power-on
Reset
Value on all
other resets
(Note1)
05h, Unbanked
T0STA
INTEDG
T0SE
T0CS
PS3
PS2
PS1
PS0
—
0000 000-
06h, Unbanked
CPUSTA
—
STKAV
GLINTD
TO
PD
—
--11 11--
--11 qq--
07h, Unbanked
INTSTA
PEIF
T0CKIF
T0IF
INTF
PEIE
T0CKIE
T0IE
INTE
0000 0000
0Bh, Unbanked
TMR0L
TMR0 register; low byte
xxxx xxxx
uuuu uuuu
0Ch, Unbanked
TMR0H
TMR0 register; high byte
xxxx xxxx
uuuu uuuu
Legend:
x
= unknown, u = unchanged, - = unimplemented read as a '0', q - value depends on condition, Shaded cells are not used by Timer0.
Note
1:
Other (non power-up) resets include: external reset through MCLR and the Watchdog Timer Reset.
Instruction
executed
MOVFP
DATAL,TMR0L
Write TMR0L
MOVFP
DATAH,TMR0H
Write TMR0H
MOVPF
TMR0L,W
Read TMR0L
MOVPF
TMR0L,W
Read TMR0L
MOVPF
TMR0L,W
Read TMR0L
Q1
Q2
Q3
Q4
Q1
Q2
Q3
Q4
Q1
Q2
Q3
Q4
Q1
Q2
Q3
Q4
Q1
Q2
Q3
Q4
Q1
Q2
Q3
Q4
AD15:AD0
ALE
WR_TRM0L
WR_TMR0H
RD_TMR0L
TMR0H
TMR0L
12
13
AB
FE
FF
56
57
58
In this example, old TMR0 value is 12FEh, new value of AB56h is written.
Instruction
fetched
MOVFP
DATAL,TMR0L
Write TMR0L
MOVFP
DATAH,TMR0H
Write TMR0H
MOVPF
TMR0L,W
Read TMR0L
MOVPF
TMR0L,W
Read TMR0L
MOVPF
TMR0L,W
Read TMR0L
MOVPF
TMR0L,W
Read TMR0L
Previously
Fetched
Instruction