6502 STATUS FLAGS
The 6502 status register contains 8 bits, each one with a different
meaning. These bits are altered and accessed by various instructions
in order to describe the current state of processing.
| 7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| N |
V |
|
B |
D |
I |
Z |
C |
- C: CARRY -
Is the "carry" of addition, or "borrow" of subtraction. The
rotation commands also use it.
- Z: ZERO -
Returns 1 if the result of the operation was zero.
- I: IRQ DISABLE -
Used to turn off interrupt requests.
- D: DECIMAL MODE -
Used to activate the decimal mode.
- B: BREAK -
Activated when a forced interrupt (BRK) occurs.
- V: OVERFLOW -
Returns 1 if the addition of two numbers of equal signals or the
subtraction of two numbers with different signs returns a result
greater than +127 or lower than -128.
- N: NEGATIVE -
Activated if the signal bit of the accumulador (bit 7) is 1.
The fifth bit was not implemented.
|
