PIC18F4580-ESLASHML datasheet(54/490 Pages) MICROCHIP

54 / 490 page

PIC18F2480/2580/4480/4580

DS39637D-page 54

5.6

Reset State of Registers

Most registers are unaffected by a Reset. Their status

is unknown on a Power-on Reset 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 5-3. These bits

are used in software to determine the nature of the

Reset.

Table 5-4 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 5-3:

STATUS BITS, THEIR SIGNIFICANCE AND THE INITIALIZATION CONDITION FOR

RCON REGISTER

Condition

Program

Counter(1)

RCON Register

STKPTR Register

SBOREN

POR BOR STKFUL

STKUNF

Power-on Reset

0000h

111

RESET Instruction

0000h

u(2)

0uu

Brown-out Reset

0000h

u(2)

111

MCLR Reset during

Power-Managed Run modes

0000h

u(2)

u1u

MCLR Reset during

Power-Managed Idle modes and

Sleep mode

0000h

u(2)

u10

WDT Time-out during Full Power

or Power-Managed Run modes

0000h

u(2)

u0u

MCLR Reset during Full-Power

execution

0000h

u(2)

uuu

Stack Full Reset (STVREN = 1)

0000h

u(2)

uuu

Stack Underflow Reset

(STVREN = 1)

0000h

u(2)

uuu

Stack Underflow Error (not an

actual Reset, STVREN = 0)

0000h

u(2)

uuu

WDT Time-out during

Power-Managed Idle or Sleep

modes

PC + 2

u(2)

u00

Interrupt Exit from

Power-Managed modes

PC + 2

u(2)

uu0

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).

Reset state is ‘1’ for POR and unchanged for all other Resets when software BOR is enabled

(BOREN<1:0> Configuration bits = 01 and SBOREN = 1); otherwise, the Reset state is ‘0’.

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