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How the Barcode module works
The Barcode module is not only made of scalable fonts. It is hooked to font calls within the
PCL5 interpreter. Typeface numbers from 24600 to 24800 (those number are in a
guaranteed exclusive range) activate the intelligence. All data mapped to one of those
special fonts is analysed and converted into bar code directly by the firmware.
If you want to print special characters (ASCII code < 32) with those bar codes, a
„Transparent Print Data" PCL sequence (Esc&p#X) must follow immediately the font
selection sequence. This is the only way to know how many characters have to be printed.
The firmware gets from the I/O port the data corresponding to the font. The end of bar
code data is determined according to the bar code type:
* Barcode data is numeric only: ended by space/CR/LF/FF/Escape code.
* Barcode data is alphanumeric: ended by CR/LF/FF/Escape code.
If you want to print binary informations in the barcode, please use the Esc&p#X length
definition sequence, explained right before.
1) Once the data is received, it is analysed to verify it fits in the bar code specs:
Correct data size, for example Code 2of5 interleaved must have an even size, EAN
and UPC have fixed lengths...)
Valid data: some systems, like UPC-E, accept only specially structured data.
If data can only be numeric or alphanumeric, it accepts only allowed characters.
2) Some code systems, like Code 128C print compressed data. The compressed value is
not always available to the user. For such codes, the Barcode module verify if data is
compressed. If not, it performs automatically the compression.
3) Some formats require what is called a checksum. A checksum is a value, result of a
complex calculation on the code data. That value is added to the end of the data and
used by the code reader to proof the reading. The Barcode module calculates
automatically the checksum(s) of bar codes which need it. Bar codes can have up to 2
checksums (MSI Plessey, UCC128). If the checksum was provided with fixed length
data (EAN 8/13, UPC) it is ignored.
The Barcode module then generates the shape of the bar code, according to
parameters in the font-like PCL sequence. For Barcode module bar codes, PCL font
parameters don't have the standard meaning (besides the V and T parameter):
The parameter definition for Barcodes:
P parameter: Controls if/how text is printed with bars
H parameter: Controls what font to use for that text
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