22 Apr
2007
22 Apr
'07
8:14 p.m.
On 22 Apr 2007 at 11:41, Roger Ivie wrote:
You could take the approach of the Atari Portfolio.
Provide some RAM
at the expected video memory address for the application to fiddle
with. Then periodically scan that RAM and copy whatever is there
to the screen.
I was involved in a similar project that took some DRAM and a Z80
with a DART and put it on an ISA card to take the place of an MDA.
The Z80 periodically scanned the buffer and generated updates to be
sent to a VT-220 compatible terminal. The board had enough smarts
to even do split-screen on the VT220, with a second mainframe
connection occupying the top window and the MDA display occupying the
bottom. It worked okay with text, but graphics was beyond its
limits.
--Chuck