>Hi all!
>I have a question.
>
>Im acessing a 16bit .dll file to read values from a PLC and have some problems the code is like this:
>
>
>SET UDFPARMS TO value
>
>SET DEFAULT TO C:\dbf\testapi
>IF !"FOXTOOLS" $ SET("library")
>SET LIBRARY TO (SYS(2004)+"FOXTOOLS")
>lLoaded = .T.
>ENDIF
>
>perstr=''
>
>Portpa = RegFn("PCDSetParameter","III","I","c:windows\system\promosvb.dll")
>Porton = RegFn("PCDOpen","","I","c:\windows\system\promosvb.dll")
>Stasjon= RegFn("PCDSetStation","I","","c\windows\system\promosvb.dll")
>LesR=
>RegFn("PCDReadRegister","IIC","I","c\windows\system\promosvb.dll")
>
>per= CallFn(Portpa,1,19200,1)
>per1=CallFn(Porton)
>per3=CallFn(Stasjon,1)
>per2=CallFn(LesR,500,1,perstr)
>
>The PCDreadregister have the following parameters
>integer adress =start adress off register in PLC
>integer count =number off registers to read
>long value =array with return values
>
>I dont know how to return a valid value I have tried with
>@ in "PCDReadRegister","II@C"
>
>I have tried with @perstr then I got an error:
>Param 2 wrong got R expected C??
>
>
>If you know please help
>
>Best regards
>
>Per Simmersholm

In addition to what Andrew said. You also need to initialize the perstr to the size of the array you need, not a null string. For example, if it needs to hold four DWORDS (4 bytes integers), you'd say:

perstr = SPACE(16)

This will make certain that the memory for the values is properly allocated.

hth,