PIC18F2420 MICROCHIP [Microchip Technology], PIC18F2420 Datasheet - Page 50

• Manufacturer Part Number: PIC18F2420
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F2420/2520/4420/4520
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:
DS39631A-page 48
Power-on Reset
RESET Instruction
Brown-out Reset
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’.
Condition
STATUS BITS, THEIR SIGNIFICANCE AND THE INITIALIZATION CONDITION
FOR RCON REGISTER
Program
PC + 2
Counter
PC + 2
0000h
0000h
0000h
0000h
0000h
0000h
0000h
0000h
0000h
0000h
(1)
SBOREN
Preliminary
u
u
u
u
u
u
u
u
u
u
u
1
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
RCON Register
RI
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.
1
0
1
u
u
u
u
u
u
u
u
u
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
 2004 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