Lexmark FORMS 249X Technical Reference page 171

Code 128
Code 128 is a flexible symbology that uses numeric and certain alphabetic and
symbolic characters. It provides three separate character sets and a method of
shifting between character sets within the same barcode. The first byte of the
data string defines the character set. If an invalid character is included for the
first byte, the printer ignores all data defined by n1, n2 and does not print the
barcode. Valid values for the first byte are x41 (for character set A), x42 (for
character set B), and x43 (for character set C). To shift to another character set,
two special codes are provided in each character set. They may be included in
the barcode data to shift to one of the two alternative character sets. If the check
digit generation flag is on (b0 = 1), the printer adds a 0 to the data string
automatically.
k value:
m value:
s value:
minimum v1, v2 values:
c parameter:
n1 value (b0 = 0):
n1 value (b0 = 1):
n2 value:
186, xBA
0 to 4, x00 to x04
-3 to 3, xFD to x03
x0E, x01 (248x)
x20, x01 (249x)
functions available:
b0, check digit
b1, human readable
2 to 255, x02 to xFF
2 to 255, x02 to xFF
0, x00
Section 8: Barcodes
171