Zenith Z-100 Series, Reference Manual

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Page 7.40
Video Graphics Programming
Custom Character Creation
Normally when in graphics mode, characters called from the computer's ROM
are the first 128 characters of the character font
In addition to these standard characters, you may create your own 128 custom
character set using the following procedure.
First allocate a I kilobyte section of user RAM to hold your characters. Eight
bytes will be needed for each character you create.
Next design each character using an 8 x 8 m atrix as shown in the example
of Figure 7.7.
COLUMN
YALUE
7 6 5 4 3 2 1 0
128 6 4 3 2 16 8 4 2
1
X
O
40
O K 3
2
BYTE 1 19 6 10 C4
BYTE 2 3 8 1 p =26 1 6
BYTE 3 2 5 1 0 = 19 1 6
BYTE 4 5 7 1 0 3 9 16
B YTE 5
=141 0 E 16
B YTE 6
= 10 1 0 = A 1 6
B YT E 7
=
1 0 1 0
=
A16
BYTE 8 2 0 1 0
=1
16
0
4
Figure 7.7. Character Design Matrix
Place a dot or fill in each location in the matrix which will be a solid part of
your character. Then add up the binary weights of the spaces used in each row
of the character grid. Note that the very first space is the MSB of each row. When
you have values for all eight rows, you have all the data needed for the first
character in your set This data will be loaded into the first 8 bytes of the memory
you have allocated for your character set