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PSHD
(SP) – $0002 ⇒ SP
Operation:
(A : B) ⇒ M
Description:
Stacks the content of double accumulator D. The stack pointer is decre-
mented by two, then the contents of accumulators A and B are stacked
at the location to which the SP points.
After PSHD executes, the SP points to the stacked value of accumulator
A. This stacking order is the opposite of the order in which A and B are
stacked when an interrupt is recognized. The interrupt stacking order is
backward-compatible with the M6800, which had no 16-bit accumulator.
Push instructions are commonly used to save the contents of one or
more CPU registers at the start of a subroutine. Complementary pull in-
structions can be used to restore the saved CPU registers just before re-
turning from the subroutine.
Condition Codes and Boolean Formulas:
S
–
None affected.
Addressing Modes, Machine Code, and Execution Times:
Source Form
PSHD
CPU12
REFERENCE MANUAL
Push Double Accumulator onto Stack
: M
(SP + 1)
(SP)
X
H
I
N
Z
–
–
–
–
–
Address Mode
INH
3B
INSTRUCTION GLOSSARY
V
C
–
–
Object Code
PSHD
Cycles
Access Detail
2
OS
MOTOROLA
6-157
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