Push To Stack - Samsung S3C9228 User Manual

SAM88RI INSTRUCTION SET
PUSH

— Push To Stack

PUSH src
Operation: 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.
Flags: No flags are affected.
Format:
opc
Examples: Given: Register 40H = 4FH, register 4FH = 0AAH, SP = 0C0H:
PUSH
PUSH
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
src
→
40H
→
@40H
Bytes Cycles
2 8
8
Register 40H = 4FH, stack register 0BFH = 4FH,
SP = 0BFH
Register 40H = 4FH, register 4FH = 0AAH, stack register
0BFH = 0AAH, SP = 0BFH
S3C9228/P9228_UM_REV1.10
Opcode Addr Mode
(Hex) dst
70 R
71 IR