MOS-6502 Specification
Table of Contents
CPU variants #
There are several variants of the 6502 CPU. The following abbreviations are used to specify compatibility:
| Variant | Available on |
|---|---|
| 6502 | 6502 |
| 60C02 | 6502, 60C02 |
| R | Rockwell 60C02 and newer Western Design Center 60C02 |
| WDC | only Western Design Center 60C02 and 65816 |
| 65816 | 6502, 60C02, 65816 |
Flags #
CPU flags. Note that on the 65816 some flags have different functions depending on the CPUs operation mode.
| Bit | Flag | Name | Description | CPU |
|---|---|---|---|---|
| 7 | N | Negative | Arithmetic operation was negative | 6502 |
| 6 | V | oVerflow | Arithmetic operation overflow | 6502 |
| 5 | 1 | unused | Unused, always 1 | 6502 |
| 5 | M | Memory | Accumulator register size | 65816 |
| 4 | B | Break | BRK was called |
6502 |
| 4 | X | indeX | Index register size | 65816 |
| 3 | D | Decimal mode | Use Binary Coded Decimal arithmetic | 6502 |
| 2 | I | IRQ disable | Prevent execution of IRQs | 6502 |
| 1 | Z | Zero flag | Arithmetic operation was zero | 6502 |
| 0 | C | Carry flag | Carry over | 6502 |
| E | Emulation | 6502 emulation mode | 65816 |
Other specifications #
2023
MOS-6502 Addressing Modes
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MOS-6502, WDC-65C01, WDC-65815 addressing modes without instruction set.