Rockwell Automation 2755 Enhanced Decoder Series B - Manual (Page 138)

10–3 Configuration: Host Message Replacement Rules
Publication 2755-833
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Rule status, located on the far left side of the screen
Each number represents an available host message replacement
rule. Currently enabled rules are marked with an asterisk (*).
Rules are enabled by assigning a value to the Find String
Containing field.
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Host message replacement rule definition, located in the upper
half of the screen
This section displays the current search rule criteria (which
include Source, Symbology, Symbol Number, and Find String
Containing) and the replacement string to send to the host when
matches are found. The rule definition also includes parameters to
fix the length of the field, the character used to “fill” the field,
and the alignment of the string within the field.
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Example testing, in the lower portion of the screen
This section provides a “worksheet” where you can insert sample
bar code strings to test the performance of your rules. This feature
allows you to conveniently “debug” your replacement rule
expressions for structural and logical errors before going on-line.
You simply input the test bar code string on the left. The string
that will appear in the host message after application of the
displayed rule appears on the right. If your test string does not
create a match, you will be notified of that fact on the right side
of the screen.
Taken together, these three sections provide for full control over
host message replacement rules, and enable you to format complete,
comprehensible message fields as required.
Each format parameter is defined below along with the field type and
possible values. The default value is shown in bold letters in the
parameter tables. A careful study of the examples that follow the
parameter descriptions will help explain their use.
Metacharacters
The decoder provides a complete set of special purpose characters
you can use to perform logical functions on characters, expressions,
or even entire strings. These characters are known as metacharacters.
Simply put, they are string manipulation commands consisting of
standard ASCII characters which you can embed within search or
replacement strings. Each metacharacter conveys a specific
instruction to the decoder software, and acts upon a clearly defined
range within the string. Metacharacters can be used with standard
alphanumeric characters to describe and manipulate even the most
complex substitution scenarios with ease.