29.1 Read-Modify-Write Operations
Any instruction that specifies a file register as part of the instruction performs a Read-Modify-Write (RMW) operation. The register is read, the data is modified, and the result is stored according to either the Working (W) register, or the originating file register, depending on the state of the destination designator ‘d’ (see Table 29-1 for more information). A read operation is performed on a register even if the instruction writes to that register.
| Field | Description |
|---|---|
| f | Register file address (0x00 to
0x7F) |
| W | Working register (accumulator) |
| b | Bit address within an 8-bit file register |
| k | Literal field, constant data or label |
| x |
“Don’t care” location (= |
| d | Destination select; d = 0: store result in W, d =
1: store result in file register f. |
| n | FSR or INDF number. (0-1) |
| mm | Pre/post increment/decrement mode selection |
| Field | Description |
|---|---|
| PC | Program Counter |
| TO | Time-Out bit |
| C | Carry bit |
| DC | Digit Carry bit |
| Z | Zero bit |
| PD | Power-Down bit |