S3C9234 Datasheet, PDF (105/214 Pages) Samsung semiconductor – 8-Bit CMOS Microcontroller

SAM88RI INSTRUCTION SET
S3C9234/P9234
PUSH — Push To Stack
PUSH
Operation:
Flags:
Format:
src
SP ¨ SP – 1
@SP ¨ src
A PUSH instruction decrements the stack pointer value and loads the contents of the source (src)
into the location addressed by the decremented stack pointer. The operation then adds the new
value to the top of the stack.
No flags are affected.
opc
src
Bytes
2
Cycles
8
8
Opcode
(Hex)
70
71
Addr Mode
dst
R
IR
Examples:
Given: Register 40H = 4FH, register 4FH = 0AAH, SP = 0C0H:
PUSH
40H
→
Register 40H = 4FH, stack register 0BFH = 4FH,
SP = 0BFH
PUSH
@40H
→
Register 40H = 4FH, register 4FH = 0AAH, stack register
0BFH = 0AAH, SP = 0BFH
In the first example, if the stack pointer contains the value 0C0H, and general register 40H the value
4FH, the statement "PUSH 40H" decrements the stack pointer from 0C0 to 0BFH. It then loads the
contents of register 40H into location 0BFH. Register 0BFH then contains the value 4FH and SP
points to location 0BFH.
6-36