SWAP

Instruction Name	Swap Bytes
Mnemonic	SWAP
CP1610 Clock Cycles	6 or 8
Interruptible	No
Opcode Range	$0040-$0047
Input Flags	None
Output Flags	Sign Flag, Zero Flag

The Swap Bytes (SWAP) instruction can perform two very different functions depending on the "double swap" indicator. A single swap trades the lowest eight bits in a register with the upper eight bits. A double swap essentially copies the lowest eight bits in a register to the upper eight bits. Regardless of which swap is specified, the CP1610 then sets or clears the Sign Flag and [[Zero Flag] according to the resulting value. The opcode format is as follows.

   0000:0000:0100:1srr

   where:
       s   indicates the type of swap
           such that:
               s == 0   indicates a single swap
               s == 1   indicates a double swap

       rr  indicates the target register
           such that:
               rr == 00   indicates register R0
               rr == 01   indicates register R1
               rr == 10   indicates register R2
               rr == 11   indicates register R3