
PIC18F2585/2680/4585/4680
DS39625C-page 48
Preliminary
2007 Microchip Technology Inc.
4.6
Reset State of Registers
Most registers are unaffected by a Reset. Their status
is unknown on POR and unchanged by all other
Resets. The other registers are forced to a “Reset
state” depending on the type of Reset that occurred.
Most registers are not affected by a WDT wake-up,
since this is viewed as the resumption of normal
operation. Status bits from the RCON register, RI, TO,
PD, POR and BOR, are set or cleared differently in
different Reset situations, as indicated in
Table 4-3.These bits are used in software to determine the nature
of the Reset.
Table 4-4 describes the Reset states for all of the
Special Function Registers. These are categorized by
Power-on and Brown-out Resets, Master Clear and
WDT Resets and WDT wake-ups.
TABLE 4-3:
STATUS BITS, THEIR SIGNIFICANCE AND THE INITIALIZATION CONDITION FOR
RCON REGISTER
Condition
Program
Counter
RCON Register
STKPTR Register
SBOREN
RI
TO
PD
POR BOR
STKFUL
STKUNF
Power-on Reset
0000h
1
111
00
0
RESET
Instruction
0000h
u(2)
0uu
uu
u
Brown-out
0000h
u(2)
111
u0
u
MCLR during Power Managed
Run modes
0000h
u(2)
u1u
uu
u
MCLR during Power Managed
Idle modes and Sleep mode
0000h
u(2)
u10
uu
u
WDT Time-out during Full Power
or Power Managed Run modes
0000h
u(2)
u0u
uu
u
MCLR during Full Power
Execution
0000h
u(2)
uuu
uu
u
Stack Full Reset (STVREN = 1)
0000h
u(2)
uuu
uu
1
u
Stack Underflow Reset
(STVREN = 1)
0000h
u(2)
uuu
uu
u
1
Stack Underflow Error (not an
actual Reset, STVREN = 0)
0000h
u(2)
uuu
uu
u
1
WDT Time-out during Power
Managed Idle or Sleep modes
PC + 2
u(2)
u00
uu
u
Interrupt Exit from Power
Managed modes
PC + 2(1)
u(2)
uu0
uu
u
Legend: u = unchanged
Note 1:
When the wake-up is due to an interrupt and the GIEH or GIEL bits are set, the PC is loaded with the
interrupt vector (008h or 0018h).
2:
Reset state is ‘1’ for POR and unchanged for all other Resets when software BOR is enabled
(BOREN1:BOREN0 Configuration bits = 01 and SBOREN = 1); otherwise, the Reset state is ‘0’.