This board incorporated static memory technology for the 8K x 8 screen
memory of the 6847 color graphics generator. With the 6847, the user could
select 10 different color modes of operation - from full alphanumeric with
semi graphics to high density graphics. Upon power-up, the SPECTRUM board
behaved as a standard high speed 8K static RAM board - capable of running at
6MHz with a Z-80 and 8MHz with an 8085 or 8088.
When graphics was required, the user alters the board programming through
the Graphics Control Port. This port not only controlled the board's
operation as a RAM board or a graphics board, but graphics density, color
set and alphanumeric/semi-graphics mode. A 75 ohm video output was
provided through an RCA type jack for direct conÂnection to a color monitor,
or through a four pin connector that can directly mated to any F.C.C.
approved modulator.
A programmable wait state generator was provided in color graphics mode to
compensate for the restricted timing requirements when the 6847 was in
operation. Full 24 bit addressing was provided so that the graphics RAM
could be removed from base page memory, and finally, a full duplex parallel
port with full handÂshaking was provided for interfacing to keyboards,
joysticks, LED's or anything requiring parallel port data.
The manual for this board can be obtained
here.
