Compuprint MDP40B Programmer Manual - Manual (Page 77)

A-75
Byte 4:
- Bit 7, 6 Graphic character description:
- 0: shading character
- 1: line drawing character
- 10: underscored character
- 11: not supported
All graphics characters are 30 dot high. An underscored character is defined
as a blank graphic (all zeros) and it is automatically generated by the printer.
A shading character repeats dots 1-6 of each column as dots 25 through 30
respectively. A line drawing character repeats dots 23 and 24 as the pairs 25
and 26, 27 and 28, 29 and 30.
- Bit 5 to 0 The number of dot columns of the character shape minus one. For example: the
character width of Draft generator is 10 dots and bit 5 to 0 must be set to 9.
- 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: