PC is subtracted from stack and replace old PC address. Then offset is added to SP value. This instruction is useful to restore reserved space memory of stored arguments at time sub-routine is called.
----------------------------------------------------------------- |15 |14 |13 |12 |11 |10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 0 | |---------------------------------------------------------------| | 16 BITS OFFSET | ----------------------------------------------------------------- "16 BITS OFFSET" is a signed 16 bits value to add to SP.