Microcom 238B Operator's Manual page 116

Downloadable Fonts
The ASCII-HEX conversion is performed by ORing the most significant and least significant
nibbles of every byte with "30" HEX.
For Example: To convert the byte "6C" to ASCII-HEX, simply OR the first and second
nibbles with "30" HEX. This results in the two bytes "36" HEX and "3C" HEX. This
conversion results in a file size that is twice as big as the source but the data can now be
transmitted over a 7-bit data connection.
7.4.3 Save FONTS to FLASH (^D135)
^A ^D COMMAND
xxyy 135 Save FONTS to FLASH.
This command is not normally seen by the user. It is put into a FONT file by
the FONT converter program which generates a special ^Axxyy^D135 code
which is placed at the beginning of the FONT download file. The ^Axxyy tells
the printer the overall size of the file according to this format:
xx = the number of additional 64KB sectors in the FONT file set
yy = CGN # (1-255)
If xx = 00, then the FONT fits into one 64Kbyte sector of memory and there
are no additional sectors required for the FONT.
If xx > 00, then the FONT is larger than one 64KB sector, and xx is the
number of ADDITIONAL 64KB sectors needed for the FONT. The xx field >
00 signals the printer to get ready for a multi-sector FONT download. Each
subsequent download contains a header with the xx field decremented by 1.
The last download file has a header field xx = 00.
EXAMPLE: ^A0124^D135
FONT download for FLASH memory is coming. The download will be 2
sectors long, and the printer will access the FONT in FLASH memory using
CGN #24 and TCI #7. The ^A0124^D135 command will be right at the
beginning of the file. So the ^D135 command is never sent by itself, it's
always in a FONT download file, and the user never really sees it.
The FONT download file may be larger than 64Kbyte. The only limit on the file
size is the amount of memory available to hold the file. When the FONT file is
created, a specific reference number, called a CGN # is assigned to the file by
the user. After the FONT file has been downloaded and stored in FLASH, the
printer retrieves the FONT from FLASH by using its CGN # and TCI #7(for
FLASH). The FONT may be stored anywhere in the printer's FLASH memory;
it is NOT restricted to a specific FLASH memory location. The printer
maintains a address table that tells where each FONT CGN # is stored in
FLASH.
The CGN # is established by the user when the FONT download file is created
using the font converter program. Since this is an arbitrary number picked by
the user, it is possible to create two separate FONT files with the same CGN
#. In fact, many FONT files could be created using the same CGN #. For the
7-4
This command tells the printer that an extended
238B Operator's Manual - 880053-0101
Chapter 7