SWAP - Revision history

Mr z: fix opcode error

2017-07-01T05:25:56Z

fix opcode error

Mr z: Protected "SWAP" ([edit=autoconfirmed] (indefinite) [move=autoconfirmed] (indefinite))

2010-12-04T09:16:18Z

Protected "SWAP" ([edit=autoconfirmed] (indefinite) [move=autoconfirmed] (indefinite))

Mr z at 16:46, 5 November 2007

2007-11-05T16:46:58Z

Mr z at 14:57, 8 October 2007

2007-10-08T14:57:53Z

Arnauld at 23:46, 14 January 2005

2005-01-14T23:46:14Z

Pingaso at 20:13, 14 January 2005

2005-01-14T20:13:42Z

Pingaso at 20:12, 14 January 2005

2005-01-14T20:12:55Z

New page

[[Category:CP1610]]
<table border>
<tr><td>Instruction Name</td><td>Swap Bytes</td></tr>
<tr><td>Mnemonic</td><td>SWAP</td></tr>
<tr><td>CP1610 Clock Cycles</td><td>6 or 8</td></tr>
<tr><td>Interruptible</td><td>No</td></tr>
<tr><td>Opcode Range</td><td>$0040-$0047</td></tr>
<tr><td>Input Flags</td><td>None</td></tr>
<tr><td>Output Flags</td><td>[[Sign Flag]], [[Zero Flag]]</td></tr>
</table><br/>
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.<br/>

0000:0000:0100:1srr<br/>
where:
s indicates the type of swap
such that:
s == 0 indicates a single swap
s == 1 indicates a double swap<br/>
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

@@ Line 16: / Line 16: @@
 The opcode format is as follows.<br/><br/>
-:0000:0100:1srr<br/>
+:0000:0100:0srr<br/>
      where:
          s   indicates the type of swap

@@ Line 9: / Line 9: @@
 <tr><td>Output Flags</td><td>[[Sign Flag]], [[Zero Flag]]</td></tr>
 </table><br/>
-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 number of clock cycles used depends on the type of swap specified.  A single swap will use 6 clock cycles and a double swap will use 8 clock cycles.<br/><br/>
+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 [[Sign Flag]] gets set based on bit 7 of the result.  This makes double-swap useful for testing the sign bit of an 8-bit value.  The number of clock cycles used depends on the type of swap specified.  A single swap will use 6 clock cycles and a double swap will use 8 clock cycles.<br/><br/>
 [[Image:Swap_diagram.png]]

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