PIC18F2221 MICROCHIP [Microchip Technology], PIC18F2221 Datasheet - Page 50

• Manufacturer Part Number: PIC18F2221
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F4321 FAMILY
4.6
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 oper-
ation. 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 4-3:
DS39689E-page 48
Power-on Reset
RESET Instruction
Brown-out
MCLR during power-managed Run modes
MCLR during power-managed Idle modes
and Sleep mode
WDT Time-out during full power or
power-managed Run mode
MCLR during full power execution
Stack Full Reset (STVREN = 1)
Stack Underflow Reset (STVREN = 1)
Stack Underflow Error (not an actual Reset,
STVREN = 0)
WDT time-out during power-managed Idle or
Sleep modes
Interrupt exit from power-managed modes
Legend: u = unchanged
Note 1:
2:
Reset State of Registers
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).
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’.
STATUS BITS, THEIR SIGNIFICANCE AND THE INITIALIZATION CONDITION
FOR RCON REGISTER
Condition
Program
PC + 2
Counter
Preliminary
PC + 2
0000h
0000h
0000h
0000h
0000h
0000h
0000h
0000h
0000h
0000h
(1)
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.
RI
1
0
1
u
u
u
u
u
u
u
u
u
RCON Register
TO
1
u
1
1
1
0
u
u
u
u
0
u
PD
1
u
1
u
0
u
u
u
u
u
0
0
POR BOR STKFUL
0
u
u
u
u
u
u
u
u
u
u
u
© 2007 Microchip Technology Inc.
0
u
0
u
u
u
u
u
u
u
u
u
STKPTR Register
0
u
u
u
u
u
u
1
u
u
u
u
STKUNF
0
u
u
u
u
u
u
u
1
1
u
u