compare double words in directsoft

guy's

is there a way to use compare statements in directsoft 5.2 on doulble word bcd numbers . i have been using some of the double word math instructions . but all the compare instructions seem to be single word bcd . i am i missing something . is there another method to compare double word numbers ?

The CMPD instruction provides this. It is an output box instruction. On execution it affects SP60, SP61, SP62 according to the results of the compare. These system bits must be used before any other instruction which may affect them. I copy the state of the relevant bits to another 'C' bit.

plc noob,

Use the compare double instruction page 5-82 in the manual

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thank you . makes sense now

bernie_carlton said:

The CMPD instruction provides this. It is an output box instruction. On execution it affects SP60, SP61, SP62 according to the results of the compare. These system bits must be used before any other instruction which may affect them. I copy the state of the relevant bits to another 'C' bit.

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I just did this last night in a program.

One other part of the instruction. You have to load one of your double words into to the accumlator stack then used the CMPD for the other double word. So basically your code looks something like this:


---------------------|--LDD v2000
|--CMPD v2002


-[sp62]--------------(out c0)


Well this is how mine looked anayway.