Rockwell Automation 2755 Enhanced Decoder Series B - Manual (Page 143)

10–8 Configuration: Host Message Replacement Rules
Publication 2755-833
The lowest numbered rule with the Host Message Field Number
value of 1 (or All) will be applied first. If that rule is successful, no
other rule specifying field 1 (or All) will be applied. This will
continue until a rule satisfies the field, or until all appropriate rules
have been applied to field 1. The decoder will continue this process
for all fields until each is satisfied, or until all appropriate rules have
failed. No-read Replacement strings (if defined) will be substituted
for the data if the rules fail. See Chapter 11.
Important: You will want to set up your host message replacement
rule table with care. Here are a few general guidelines:
•
Prioritize your replacement rules. Only one rule can fill a field,
and once one rule has filled a field, then no other rules will apply
to that field. Define the rule which will lead to the most
preferable result first, the next preferable result next, and so on.
•
If you need to fill specific fields, define the rules for those fields
first.
•
When using metacharacters, define first those expressions which
are most restrictive (most specific), and then proceed to those
which are less so.
•
Define rules specifying All as the host message field number last.
This is especially important, because if such a rule creates a
match, then no other rules that occur after it and are directed to
specific host fields can have any affect. (Remember: once one
rule has filled a field, then no other rules will apply to that field.)
Source
Field Type Options
Select
A (Default for DS Only)
B
A|B = A or B (Default for DD only)
Aux
Specifies where an event can originate and meet the host message
replacement rule requirements. For DS decoders, Scanner A is the
default value. For DD decoders, the default value is A|B, which
means that the decoder will accept input from either A or B to create
a match. You can also select AUX or, if you have a DD decoder,
Scanner B as the source.
The decoder processes rules for the AUX and each of the scanners
separately. For example, if all enabled rules specify Scanner A as the
source, then data received from Scanner B or the auxiliary terminal
does not pass through the rules and will not be affected by them.
Configuration Parameters