Internet PLC Forum
General => Technical support => Topic started by: cch1955 on September 20, 2007, 03:49:19 PM
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Great one:
Any plan for more than 8 sequencers?
Thanks
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So far we never receive any request for more than 8 sequencers. Most users would use only 1 or 2 sequencers. It is interesting to know how are you going to use so many sequencers. Of course if you are using M-series PLC you could implement more sequencer using TBASIC. i.e. A TBASIC custom function can be programmed to set some relays to ON based on the PV of a counter.
Some PLCs that do not have sequencers actually use a "Shift Register" to perform job similar to a sequencer. You could put in a bit and then apply LEFTSHIFT or RIGHTSHIFT to shift the bit along one or more internal relay variable RELAY[n] . The relay bit that is turned ON will indicate the step position. You can implement as many of these as the memory and relay space permits. Since you can cascade multiple RELAY[] you could have sequence that are larger than 32 steps since each RELAY[] variable cover 16-bits.
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Great! I never know still have this two method to implement the sequencers:
1) A TBASIC custom function can be programmed to set some relays to ON based on the PV of a counter.
2) You could put in a bit and then apply LEFTSHIFT or RIGHTSHIFT to shift the bit along an internal relay. The relay bit that is turned ON will indicate the step position.
Previously, I used large number of counters to implement the sequencers after full used of 8 sequencers.