Rockwell Automation 2755 Enhanced Decoder Series B - Manual (Page 149)

10–14 Configuration: Host Message Replacement Rules
Publication 2755-833
Assembling a Host Message
Some applications demand nothing more than a stream of raw bar
code data to be of use. However, interpretation and manipulation of
that raw data proves useful in many production situations. Host
message replacement rules make that interpretation and manipulation
possible.
When assembling a host message, the decoder software calls upon
the rule processor to fill in each position of the host message
beginning with the first host message field, and proceeding in order
to the last.
Up to 16 fields can be specified for each message. The exact number
is determined by the setting in the Host Message Format screen’s
number of fields in host message.
If the number of fields in host message value is All, then the number
of fields in the host message will equal the value appearing in the
Symbols per Package parameter on the Scanner Control screen.
However, when its value is 1 to 16, then the decoder sends back
exactly that number of fields.
In a case where the number of fields read does not equal the
specified number of symbols per host message, the host replacement
rules, if active, will determine which data is sent to the host. If the
rules are inactive, symbol data will be sent in the order decoded, up
to the value specified in the number of fields in the Host Message
parameter. In cases where there are fewer symbols than there are
fields specified, then the decoder will send no-read message strings
as explained below.
If no rule finds a match for a given host message field, it inserts the
no-read replacement string for that field number. In cases where the
no-read replacement string has not been defined for that particular
field number, then the decoder inserts the default no-read string.
Finally, if the default no-read string is not defined, then the decoder
leaves the field blank.