|
 |
The Memotech MTX Series |
 |
The FDX 80 Column Graphics Card
The Motorola
MC6845 CRTC - continued
FDX 80 Column Card Design
The 80C card uses a number of I/O ports to
interface to the 6845
|
Port |
Bit |
R/W |
Function |
|
30 |
D0 |
W |
D0 to D7 corresponds to A0 to A7
Writing to this port initiates a
VDU memory access
|
| to |
| D7 |
|
31 |
D0 |
W |
D0 to D2 corresponds to A8 to A10
|
| D1 |
| D2 |
|
D3 |
- |
Not Used |
|
D4 |
- |
Not Used |
| D5 |
W |
Write
enable attribute memory (ATRWE) |
| D6 |
W |
Write
enable ASCII memory (ASCWE) |
| D7 |
W |
Write
cycle when high/read when low |
|
32 |
D0 |
R/W |
D0 to D7 correspond to ALPHA or GRAPHIC character codes bits 0
to 7
|
| to |
| D7 |
|
Attribute Byte |
| |
Monochrome Display |
Colour Display |
|
33 |
D0 |
R/W |
Underline |
Red
foreground |
| D1 |
(no effect) |
Green foreground |
| D2 |
Bright Up |
Blue foreground |
| D3 |
(no effect) |
Red
background |
| D4 |
Reverse Video |
Green background |
| D5 |
Background |
Blue background |
| D6 |
Blink |
Blink |
| D7 |
Graphics Mode |
Graphics Mode |
|
Bit Level Ports
- Refer to the
MC8645 Datasheet |
| 38 |
(5
bits) |
Pointer to 8645
Register File Address |
| 39 |
(8
bits) |
Data to/from target
8645 Register File Address |
MC6845 Display Generation <
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The
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