Table of Contents
Advertisement
31.4.1.3 Mode control register
The mode control register is write-only. When individual bits are set, they
have the following effects:
Bit
Effect
7
Not used
6
Not used
5
Enable blink
4
High resolution mode (640x200)
3
Enable video
2
Select B&W
1
Select graphics
0
Select 80x25 text
31.4.1.4 Colour select register
The colour select register is not implemented, as MP2500's display is only
monochrome.
31.4.1.5 Status register
The status register is a read-only register which returns the adaptor's status
by setting individual bits as follows:
Bit
Significance
7
Not used
6
Not used
5
Not used
4
Not used
3
Vertical retrace
2
Lightpen switch made
1
Lightpen trigger set
0
Display enabled
Bits 0 and 3 change each time they are read, returning 1xx1, 0xx1, 1xx0,
and then 0xx0 before the pattern repeats. Bit 0 is usually checked by
programs to time updates to the CGA RAM (to avoid display 'snow'), but
there is no 'snow' problem with the MP2500 CGA.
298
Implemented?
Implemented?
H
MP2500 System Developer's Guide
USKY
-
-
N
Y
N
N
Y
Y
-
-
-
-
Y
N
N
Y
Advertisement
Table of Contents
Troubleshooting
