Can we set 'NELM' tobe a variable in waveform or subArray?

[=?gb18030?b?S2V2aW4=?= via Tech-talk <tech-talk at aps.anl.gov>]

Hello everyone,

    

I used waveform to read  8 channels data, the waveform record is:

record(waveform, "$(P)Countxxyy")

{

  field(DTYP, "stream")

  field(INP, "@ct0801f.proto Counters_in  $(PORT)")

  field(NELM, "8")

  field(FTVL, "LONG")

  field(SCAN, "$(SCAN)")

}

The user hope that the NELM is a variable,  so I used $(P)N  to controller the readout numbers:

record(waveform, "$(P)Counters")

{

  field(DTYP, "stream")

  field(INP, "@ct0801f.proto Counters_in  $(PORT)")

  field(NELM, "$(P)N")

  field(FTVL, "LONG")

  field(SCAN, "$(SCAN)")

}

 When $(P)N changed, the $(P)Countxxyy keep an initial value. I think that the NELM can not be modified:

Then I found the modify property about NELM in subArray is ¡®yes¡¯,

So I changed the record like this:

record(waveform, "$(P)Counters")

{

  field(DTYP, "stream")

  field(INP, "@ct0801f.proto Counters_in  $(PORT)")

  field(NELM, "8")

  field(FTVL, "LONG")

  field(SCAN, "$(SCAN)")

}

record(subArray,"$(P)Countersxy") {

  field (DESC, "Read counterx~countery")

  field (INP, "$(P)Counters")

  field (MALM, "8")

  field (NELM, "$(P)N")

  field (INDX, "0")

  field (SCAN, "$(SCAN)")

}

When the $(P)N changed tobe 4, $(P)Countersxy.NELM doesn't change. It is still the inital value 1, and $(P)Countersxy read only 1 channel data.

Can we set the NELM tobe a variable?

How could we read changing channels from the above 8 channel datas?

I am confused and ask for help. Thank you so much.

With my best reguards,

Kevin