37.1 Read-Modify-Write Operations
Any WRITE 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
the table below 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 | Prepost 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 |