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CHAPTER 7 DETAILED EXECUTION INSTRUCTIONS
7.74 ST (Store Word Data in Register to Memory)
Subtracts 4 from the value of "R15", stores the word data in dedicated register "Rs" to
the memory address indicated by the new value of "R15".
If a non-existent dedicated register is given as "Rs", undefined data will be transferred.
■ ST (Store Word Data in Register to Memory)
Assembler format: ST Rs, @ – R15
Operation: R15 – 4 → R15
Rs → (R15)
Flag change:
N, Z, V, and C: Unchanged
Execution cycles: a cycle(s)
Instruction format:
Example: ST MDH, @ – R15
NZVC
––––
MSB LSB
000101111000 Rs
12345670
R15R15
8765 4321
8765 4321
12345670
12345674 12345674
1234 5678
8765 4321
MDH
1234 5674
MDH
xxxx xxxx
Memory Memory
Before execution After execution
Instruction bit pattern : 0001 0111 1000 0100