STZ
Store Zero to Memory
Stores zero to memory.
On all processors, the data written to memory is 8-bit. However, for 16-bit processors with the m flag is clear then the data written is 16-bit with the low-order 8-bits at the effective address and the high-order 8-bits at the effective address plus one.
Flags Affected
| None. |
Instructions
| Syntax | Opcode | Available on: | # of | # of | Addressing Mode | ||
|---|---|---|---|---|---|---|---|
| (hex) | 6502 | 65C02 | 65816 | bytes | cycles | ||
| STZ addr | 9C | x | x | 3 | 41 | Absolute | |
| STZ dp | 64 | x | x | 2 | 31, 2 | Direct Page | |
| STZ addr,X | 9E | x | x | 3 | 51 | Absolute Indexed X | |
| STZ dp,X | 74 | x | x | 2 | 41, 2 | Direct Page Indexed X | |
Notes:
- 65816: Add 1 cycle if m=0 (16-bit memory/accumulator)
- 65816: Add 1 cycle if low byte of Direct Page register is not 0
Last modified November 5, 2021: Add instruction categories (6b74ff9)