Compuprint MDP 30FB Programmer's Manual page 74

- Bit 5 to 9 Compression mask description. It is used to optimize the memory occupation
and it is based on the concept that a dot column on its left is not stored. You
can calculate the compression mask of a character only after designing the
entire character. Every bit is associated with a dot column with the bit 7 of
byte 5 associated with the leftmost column. The bit is set to {1}, if the column
is equal to the preceding one; otherwise, it is set to {0}. If the character is
longer than 39 dot columns the remaining dot columns must be stored
without compression. The bit 40 (bit 0 of byte 9) must be 0. If no compression
is present in the character, byte 5 to 9 is composed by all zeros.
If you wish to copy an entry over another entry so that two characters with the same
characteristics and different code are present in the same look up table, the DLL
sequence ESC = n m id p t has the following meaning:
n and m Indicate the byte number of the sequence n is the low part and m is the high
part.
id:
Indicate the printer model. The id related to your printer is 23H.
p and t Indicate the memory address of the character that you wish to replace. p is
the low part and t is the high part.
Data Is the entry 9 bytes of the character that you want to position at address
specified by p and t.
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