Processor Status Register
From NES Hacker Wiki
The Processor Status Register (P) is a 1 byte register with each bit representing a flag. These flags are used to indicate whether something has or has not occurred based on the result of an instruction.
- Change - This flag will either be set or cleared based on the operand.
- Ignore - This flag will not change.
- Set - This flag will always be set to on, that is, have a value of 1.
- Clear - This flag will always be set to off, that is, have a value of 0.
|7||N - Negative Flag|
|6||V - Overflow Flag|
|5||1 - Always 1 Flag|
|4||B - Break Flag|
|3||D - Decimal Flag|
|2||I - Interrupt Flag|
|1||Z - Zero Flag|
|0||C - Carry Flag|