A <- A - r
SUB
r
| b7 | b6 | b5 | b4 | b3 | b2 | b1 | b0 |
|---|---|---|---|---|---|---|---|
| 1 | 0 | 0 | 1 | 0 | r | ||
The contents of register r are subtracted from the contents of the Accumulator, and the result is stored in the Accumulator. The r symbol identifies the registers A, B, C, D, E, H, or L, assembled as follows in the object code:
| Register | r | Hex |
|---|---|---|
| A | 111 | $97 |
| B | 000 | $90 |
| C | 001 | $91 |
| D | 010 | $92 |
| E | 011 | $93 |
| H | 100 | $94 |
| L | 101 | $95 |
| S | is set if result is negative, otherwise it is reset. |
| Z | is set if result is 0, otherwise it is reset. |
| H | is set if borrow from bit 4, otherwise it is reset. |
| P/V | is set if overflow, otherwise it is reset |
| N | is set. |
| C | is set if borrow, otherwise it is reset. |
If the Accumulator contains $44 and Register C contains $11, then upon the execution of
SUB C
the Accumulator contains $33.