All devices have a 16-level by 15-bit wide hardware stack. The stack space is not part of
either program or data space. The PC is PUSHed onto the stack when the
CALL or CALLW instructions are executed or an
interrupt causes a branch. The stack is POPed in the event of a RETURN,
RETLW or a RETFIE instruction execution. PCLATH is not
affected by a PUSH or POP operation.
The stack operates as a circular buffer if the STVREN Configuration bit is programmed to
‘0’. This means that after the stack has been PUSHed sixteen times,
the seventeenth PUSH overwrites the value that was stored from the first PUSH. The
eighteenth PUSH overwrites the second PUSH, and so on. The STKOVF and STKUNF flag bits
will be set on an Overflow/Underflow, regardless of whether the Reset is enabled.
1’, the device will be reset if the
stack is PUSHed beyond the sixteenth level or POPed beyond the fist level, setting the
appropriate bits (STKOVF or STKUNF, respectively).CALL, CALLW,
RETURN, RETLW and RETFIE
instructions or the vectoring to an interrupt address.