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CHAPTER 7 DETAILED EXECUTION INSTRUCTIONS
7.75 ST (Store Word Data in Program Status Register to Memory)
Subtracts 4 from the value of "R15", stores the word data in the program status (PS) to
the memory address indicated by the new value of "R15".
■ ST (Store Word Data in Program Status Register to Memory)
Assembler format: ST PS, @ – R15
Operation: R15 – 4 → R15
PS → (R15)
Flag change:
N, Z, V, and C: Unchanged
Execution cycles: a cycle(s)
Instruction format:
Example: ST PS, @ – R15
NZVC
––––
MSB LSB
0001011110010000
12345670
R15R15
FFF8 F 8 C0
FFF8 F 8 C0
12345670
12345674 12345674
123 4 5678
FFF8 F 8 C0
PS
123 4 5674
PS
xxxx xxxx
Memory Memory
Before execution After execution
Instruction bit pattern : 0001 0111 1001 0000