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Bits
4 3
o
0
Data unmodified.
o
I
Data AND'ed with latched data.
I 0
Data OR'ed with latched data.
I I
Data XOR'ed with latched data.
Data may be any of the choices selected by the Write Mode
Register except processor latches.
If
rotated data is selected, the
rotate applies before the logical function.
Read Map Select Register
This is a write-only register pointed to by the value in the
Graphics 1 and 2 address register. This value must be hex 04
before writing can take place. The processor output port address
for this register is hex 3CF.
Read Map Select Register Format
Bit
7
6
5
4
3
2
1
0
Bit O-Bit 2
Mode Register
~
Map Select 0
Map Select 1
Map Select 2
Not Used
~
Map Select-These bits represent a binary
encoded value of the memory plane number from
which the processor reads data. This register has
no effect on the color compare read mode
described elsewhere in this section.
This is a write-only register pointed to by the value in the
Graphics 1 and 2 address register. This value must be hex 05
50 IBM Enhanced Graphics Adapter
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