Determining the Cause of a Reset

Upon any Reset, multiple bits in the STATUS, PCON0 and PCON1 registers are updated to indicate the cause of the Reset. The following tables show the Reset conditions of these registers.

Table 1. Reset Status Bits and Their Significance
STKOVF STKUNF RWDT RMCLR RI POR BOR TO PD MEMV Condition
0 0 1 1 1 0 x 1 1 1 Power-on Reset
0 0 1 1 1 0 x 0 x u Illegal, TO is set on POR
0 0 1 1 1 0 x x 0 u Illegal, PD is set on POR
0 0 u 1 1 u 0 1 1 u Brown-out Reset
u u 0 u u u u 0 u u WDT Reset
u u u u u u u 0 0 u WDT Wake-up from Sleep
u u u u u u u 1 0 u Interrupt Wake-up from Sleep
u u u 0 u u u u u 1 MCLR Reset during normal operation
u u u 0 u u u 1 0 u MCLR Reset during Sleep
u u u u 0 u u u u u RESET Instruction Executed
1 u u u u u u u u u Stack Overflow Reset (STVREN = 1)
u 1 u u u u u u u u Stack Underflow Reset (STVREN = 1)
u u u u u u u u u 0 Memory Violation Reset
Table 2. Reset Conditions for Special Registers
Condition Program Counter STATUS Register PCON0 Register PCON1 Register
Power-on Reset 0 ---1 1000 0011 110x ---- --1-
Brown-out Reset 0 ---1 1000 0011 11u0 ---- --u-
MCLR Reset during normal operation 0 -uuu uuuu uuuu 0uuu ---- --1-
MCLR Reset during Sleep 0 ---1 0uuu uuuu 0uuu ---- --u-
WDT Time-out Reset 0 ---0 uuuu uuu0 uuuu ---- --u-
WDT Wake-up from Sleep PC + 1 ---0 0uuu uuuu uuuu ---- --u-
Interrupt Wake-up from Sleep PC + 1(1) ---1 0uuu uuuu uuuu ---- --u-
RESET Instruction Executed 0 ---u uuuu uuuu u0uu ---- --u-
Stack Overflow Reset (STVREN = 1) 0 ---u uuuu 1uuu uuuu ---- --u-
Stack Underflow Reset (STVREN = 1) 0 ---u uuuu u1uu uuuu ---- --u-
Memory Violation Reset 0 -uuu uuuu uuuu uuuu ---- --0-

Legend: u = unchanged, x = unknown, — = unimplemented bit, reads as ‘0’.

Note:
  1. 1.When the wake-up is due to an interrupt and Global Interrupt Enable (GIE) bit is set, the return address is pushed on the stack and PC is loaded with the interrupt vector (0004h) after execution of PC + 1.
Parent topic: Resets