Register String Format

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Introduction

In many types of PLC there is no standard way to store string values in registers. For example, in a Modbus PLC strings could be stored:

The length of the string could be determined by:

The Register String Format tells Fernhill SCADA how to retrieve a string from a PLC.

Syntax

The Register String Format has this syntax:

register-string-format ::=
  [ register-string-format-clause { , register-string-format-clause }

register-string-format-clause ::=
  format-clause
  | encoding-clause
  | packing-clause

format-clause ::=
  Format = { 'NullTerm' | 'SpaceTerm' | 'ByteLength' }

encoding-clause ::=
  Encoding = { 'ASCII' | 'UTF8' }

packing-clause ::=
  Pack = { 'None' | 'HighLow' | 'LowHigh' }

Where to Use an Register String Format in Fernhill SCADA

You can use an Register String Format in the StringFormat property of these tag types:

Examples

  1. The string "Stopped" is encoded in word registers as: 5374h 6F70h 7065h 6400h. The Register Format String to extract this string would be:
    Format=NullTerm, Encoding=ASCII, Pack=HighLow
    .
  2. The string "Stopped" is encoded in word registers as: 0753h 746Fh 7070h 6564h. The Register Format String to extract this string would be:
    Format=ByteLength, Encoding=ASCII, Pack=HighLow
    .
  3. The emoji character Emoji symbol showing a code face is encoded in word registers as: 04F0h 9FA5h B600h. The Register Format String to extract this string would be:
    Format=ByteLength, Encoding=UTF8, Pack=HighLow
    .

Further Information

Drivers

To learn about the drivers that support this property.

Fernhill SCADA Concepts

To learn about other Fernhill SCADA Concepts.

Glossary

For the meaning of terms used in Fernhill SCADA.