Rockwell Automation 2755 Enhanced Decoder Series B - Manual (Page 79)

6–6 Configuration: Symbology
Publication 2755-833
Code 128
Field Type Options
Select
No
Yes
Enables/disables decoding of Code 128 labels. The default of No
disables decoding of this symbology. Select Yes to enable decoding.
Code 128 Specific Lengths
Field Type Options
Edit Numeric 0 through 64 (0)
Sets length checking for Code 128 labels. The default is 0, which
means the decoder does not check lengths.
You can specify up to 8 code lengths (maximum of 64 characters).
The code length does not include the check character or the start
and stop characters.
① If you specify a code length other than 0, the
decoder will only decode labels with the number of characters
specified.
The decoder uses the specific length parameter in three ways:
•
The decoder discards decoded symbols with lengths that do not
match the specific length parameter
This allows you to filter out all decoded symbols except those
that have a specific length that appears in the specific length
table.
•
The decoder uses it to determine if the number of bar to space
transitions that occur during a scan is appropriate for the
symbologies and specific length values
Scans that occur in the absence of a symbol or part of a symbol
are not valid, and therefore result in extra processing overhead for
the decoder. The decoder discards these scans before the
microprocessor sees them.
•
Once the microprocessor sees a scan, it uses the specific length
parameter to search within the symbol for a valid number of bar
to space transitions
① The decoder will ignore Code 128 FNC2, FNC3, and FNC4 characters regardless of the Code 128 FN
Character setting. FNC2, FNC3, and FNC4 are also ignored by the specific length parameter.