Microcom LDS II, Programming Manual

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Chapter 5 Bar Codes
LDSII Programming Guide - 880015-0123 67
Figure 19 Code 128 Subset Switching
Subset A
This subset contains 106 unique characters, which includes numbers 0 through 9, the
English alphabet (uppercase only), punctuation marks, ASCII control codes, and the special
function codes listed in table 6.
Subset B
This subset contains 106 unique characters, which includes numbers 0 through 9, the
English alphabet (both uppercase and lower case), punctuation marks, and the special
function codes listed in table 6. This is the default if a subset is not defined when using
manual compression.
Subset C
This subset contains 106 unique characters, which includes matched pair numbers 00
through 99 and the special function codes listed in table 6. Subset C requires that an even
amount of digits to be sent because the matched pairs are encoded as a single character.
This allows for a greater amount of compression than subsets A and B. If an odd amount of
digits and/or non-numeric characters were sent while using subset C, the resulting bar code
produced would be invalid.
CI text equivalent codes: @code128, @c128
5.2.3 Code 128 (Automatic Compression)
The Code 128 bar code is a variable length, high density, alphanumeric symbology that is
extensively used worldwide. This bar code uses three subsets (A, B, and C) which allows
for the encoding of the full 128 ASCII character set along with special control codes. This
bar code uses automatic compression, which means that the printer will automatically
choose the most efficient subset and insert the appropriate special function code listed in
table 6. It is possible to force a subset change by inserting the appropriate code while in
automatic compression but is not recommended. Please note that if a subset is forced while
using automatic compression the printer will automatically switch to subset C if 6 or more
numeric characters are contained in the data string. Once the even number of characters
has been processed, the printer will then switch to subset B. This could create problems if a
user sent 6 numeric charact
ers while forcing subset A (“#7123456”), the printer would
actually automatically switch to subset C and then back to subset B resulting in an
undesired bar code. If specific control of the subsets is a requirement, then the manual
compression bar code should be used.
CI text equivalent codes: @code128auto
ABC #3 012345 #5 abc
Data String using Manual Compression
The printer
defaults to
subset B
The “#3” code, while
in subset B, switches
to subset C.
The “#5” code,
while in subset
C, switches to
subset A.