Chapter
3.
Instruction
Set
the high-order register
of
the
pair. POP then increments the stack pointer again so
that
it addresses the next
older item on the stack.
Opcode
Operand
POP
{L}
The operand may specify the B&C, D&E,
or
the
H&L
register pairs. POP
PSW
is
explained '>eparately.
Cycles:
States:
Addressing:
Flags:
POP
PSW
P 0 0
~
3
10
register indirect
none
POP
PSW
use'>
the
contents
of
the memory location specified by the stack pointer to restore the condition flags.
POP
PSW
increments the stack pointer by one and restores the
contents
of
that
address to the accumulator.
POP then increments the stack pointer again so that
it
addresses the next older item on the stack.
Example:
c==_1
_________
0 0
~
Cycles:
Stdles:
Addressing:
Flag'>:
3
10
register indirect
l,S
,P
,CY
,AC
A"ume
that a 'iubroutine
is
called because
of
an
externdl interrupt.
In
generdl, such subroutines should
SJve
and
restore
any registers
it
uses
so
that
main program
Cdn
continue
normally when
it
regaim control. The foliowing
sequence
of
PUSH and POP instructions save and re,tore the Program Status Word and all the registers:
343
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