IBM RT Series Hardware Reference Manual page 315

TNL SN20-9844 (March 1987) to 75X0235
Extended Monochrome Graphics Display Adapter Diagram
...
...
..oIL
...
1/0 CHANNEL
CRT REFRESH
X ADR
24 BIT ADR
~
DISPLAY BIT MAP
-A.
.... ...
....
-:-: .. -:.-: ..
:~
VIDEO DATA
"-'-
/ /
/~
BAMDA
Y ADR'"
. .
V--v
ADDRESS
.~
/:
.~
V
..
:r-:.r-:/.:/.:~
V
..
Video
v
~tO
1024 X 768 PELS
v
(BAMDA)
~ Video Out Syncs
16 BIT
DATA BUS
Control
..
32K Bytes
. .
~:~ HIDDEN AREA
/
~
LFG
~
-Cursor
- Raster Parameters
-Pointers
-BLT Area
GRAPHIC
OPERATION
[ 1111111111111
Instruction
ROM
Processor
Figure 1. Extended Monochrome Graphics Display Adapter Block Diagram
The Extended Monochrome Graphics Display Adapter consists of 7 major components:
1. The I/O channel interface logic which communicates with the I/O channel and allows the
system to control the display functions.
2. The BAMDA address logic which controls access to the bit map and converts system
addresses to bit map X and Y coordinates.
3. The BAMDA bit map memory which is divided into a display bit map and a hidden area
memory.
Extended Monochrome Graphics Adapter 3