commodorejohn@gmail.com wrote:
I have a question about an Apple expansion card. It came with my IIGS,
which I got at a garage sale with no documentation, and it has a card
in it that I really have no idea what it might be. At first glance, it
seems like a SCSI controller - it's a long expansion card with a DB25
connector. But part of the cable running to the connector splits off
to a second board, which doesn't go in an expansion slot, but plugs
into the game port instead. The second board has two RCA-type
connectors on it, and an Ethernet-type connector. Does anyone have any
idea what in the world this thing is? I sure don't.
Pictures, left large for easy identification!
The main board: http://img140.imageshack.us/img140/3576/boardlb9.jpg
The second board:
http://img140.imageshack.us/img140/7340/daughterboardga7.jpg
A picture of the way the two connect, and the game port plug:
http://img140.imageshack.us/img140/8383/connectiondu3.jpg
The DB25 connector, nothing special:
http://img114.imageshack.us/img114/5514/boardconnectorpq8.jpg
The crazy connectors on the second board:
http://img114.imageshack.us/img114/6047/daughterconnectorssp0.jpg
If anybody knows what this is, I'd love to hear about it!
The silkscreened "TOPSCREEN", plus the SED1341F chip (an LCD controller)
suggests that this is a controller for an LCD panel. (I couldn't find a
datasheet on this particular controller, but the SED1351F appears to be
quite similar.)
The two 8KB SRAMs provide 16KB of graphics memory for the controller
chip. This would support a 512x256 binary display, or a 256x256
4-tone grayscale display.
The front-side photo shows only a connection to +5v, so the Apple II
address lines and I/O Select are not used by the card. This is unusual
since the microprocessor generally addresses the video RAM. A back-side
photo would show whether the data lines and /DEVSEL are used, though
without address lines, these would be less useful.
So there is a chance that the card only plugs into an Apple II slot
to tap power!
On the other hand, there must be a datapath to load the video SRAMs.
This could be done with a simple "sync" signal provided through
/DEVSEL followed by putting the data on the data lines by a 16K-
iteration loop, assuming that the controller chip supports an
address counter for this purpose. Weird, but possible.
The eight wires connecting the main board to the secondary board appear
to be directly connected (through filters) to the RJ-45 connector, which
provides the connection to drive the LCD panel.
Although you suggest that the 16-pin DIP plug/socket combo plugs into
the Apple game port, that is not necessarily so. It could also plug
into any 16-pin DIP socket with the removed IC being placed into the
socket on top. This is a common way of "tapping" signals on the main
board that are not presented to the slots. (Of course, there aren't
many socketed 16-pin DIPs on IIgs boards...)
I'd guess that these signals are outputs to the secondary board, which
appears to be analog (video?) circuitry driving the two RCA connectors.
(It could be audio outputs, but I doubt it.) Perhaps one RCA connector
is an input for the Apple video, and the other is a monitor output, and
this is some kind of video switch...
To use this card you will need a compatible LCD panel, plus the software
designed to control it.