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RASELO : Refresh Address Selection (Output)
This signal is an input selection signal to the V-RAM
address multiplexer.
If this is low, the display refresh address lines
(RA051-RA121) are selected and supplied to the V-RAM.
If it
is high, the I/O bus address lines are selected and supplied
to the V-RAM.
CCOI-CC71 : Character Code Data Bus (Input/Output)
These lines are data bus from/to the even address V-RAM.
The even address of the V-RAM is used to store the character
codes in the TEXT mode.
ATOI-AT71 : Attribute Data Bus (Input/Output)
These lines are data bus from/to the odd address V-RAM.
The odd address of the V-RAM is used to store the attribute
codes in the TEXT mode.
0.5.3 Character generator(CG) signals (16 lines)
CGAI : CG Address Latch (Output)
This signal is used to set the character code read out from
the V-RAM in the external latch.
The set timing of the
external latch circuit is at the raising edge of this
signal.
The output from the external latch circuit is used
for the address of the CG-ROM.
As the character code is of
8-bit, it can select one of the 256 characters.
ROM Address : (Output)
The following 6 signals are also used as CG-ROM address
apart from the above mentioned character code which are
latched in CGAI.
CGMOI ••••• Plasma Font Selection (Not used)
INTENI ••.•• Single Dot Font Selection
RSAOl, 11, 21, 31 •.••• Raster Scan Address
The CG-ROM in this system has the capacity of 8 Kbytes, and
it contains the fonts as floowsJ
8x8 single dot character set
8x8 double dot character set
o -
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