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Graphics 2 Position Register
This is a write-only register. The processor output port address
for this register is hex 3CA.
Graphics II Position Register Format
Bit
7
6
5
4
3
2
1
0
1111111~
Position 0
Position 1
Not Used
Bit O-Bit 1
Position-These 2 bits are binary encoded
hierarchy bits for the graphics chips. The
position register controls which 2 bits of the
processor data bus to which each chip responds.
Graphics 2 must be programmed with a position
register value of 1 for this card.
Graphics 1 and 2 Address Register
This is a write-only register and the processor output port address
for this register is hex 3CE.
Graphics 1 and 2 Address Register Formats
Bit
7
6
5
4
3
2
1
0
I I I I
:
Graphics Address
Not Used
Bit O-Bit 3
Graphics 1 and 2 Address Bits-This output loads
the address register in both graphics chips
simultaneously. This register points to the data
register of the graphics chips.
46 IBM Enhanced Graphics Adapter
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