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SAM88RI INSTRUCTION SET S3C9228/P9228
6-36
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:
Bytes Cycles Opcode
(Hex)
Addr Mode
dst
opc src 2 8 70 R
8 71 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.