Push Low Accumulator Onto Stack
PUSH
7-141
Assembly Language Instructions
Syntax
PUSH
Operands
None
Opcode
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
0
1
1
1
1
0
0
0
1
1
1
1
1
0
1
Execution
Increment PC, then...
Push all stack locations down one level
ACC(15:0)
→
TOS
Status Bits
None
Description
The stack values move down one level. Then, the content of the lower half of
the accumulator is copied onto the top of the hardware stack.
The hardware stack operates as a last-in, first-out stack with eight locations.
If more than eight pushes (due to a CALA, CALL, CC, PSHD, PUSH, TRAP,
INTR, or NMI instruction) occur before a pop, the first data values written are
lost with each succeeding push.
Words
1
Cycles for a Single PUSH Instruction
ROM
DARAM
SARAM
External
1
1
1
1+p
Cycles for a Repeat (RPT) Execution of a PUSH Instruction
ROM
DARAM
SARAM
External
n
n
n
n+p
Example
PUSH
Before Instruction
After Instruction
ACC
X
7h
ACC
X
7h
C
C
Stack
2h
Stack
7h
5h
2h
3h
5h
0h
3h
12h
0h
86h
12h
54h
86h
3Fh
54h
Cycles