Husky MP2500 Manual page 319

31.4.1.2 6845 registers
The 6845 CRT controller is the core of the CGA. It has 19 internal registers,
which are accessed by writing the internal register number to the 6845
index register, then reading or writing the 6845 data register.
The 6845 internal registers are implemented as follows:
Register
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
The cursor start and end registers specify the size of the cursor by
specifying which lines it starts and ends on. The cursor address registers
specify the position of the cursor, as the character number (in the range
0..1999). Both these functions are also provided via INT 10H.
Standard texts advise that the other 6845 registers should not be accessed
directly, so the fact that they are not emulated should not cause
compatibility problems.
Chapter 31: Hardware
Access Description
W Horizontal total
W
Horizontal displayed
W Horizontal sync
W Horizontal sync width
W Vertical total
W Vertical total adjust
W Vertical displayed
W Vertical sync position
W Interlace mode
W Max scan line address
W Cursor start
W Cursor end
W Start addr (H)
W End addr (H)
RW Cursor addr (H)
RW Cursor addr (L)
R Lightpen (H)
R Lightpen (L)
Implemented?
N
N
N
N
N
N
N
N
N
N
Y
Y
Y
Y
Y
Y
N
N
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