[GreenKeys] MCT S-100 Serial board - Ever seen one? CL and/or RS-232?

[Steve Garrison]

Don't readily recognize that board, but having been in on the ground floor of the S100 Altair/Imsai age I can tell you that all the serial I/O boards I worked with were all RS232 and none were current loop (not that there couldn't have have been a couple).  I do recognize the UART chips, they were one of the standard chips of the day.  I also never ran across any memory mapped I/O boards.

And that board really looks like it had a major heat problem on the lower left at one time. Can tell if it was the power buss that was involved, but pin 1 & 51 were +8 volts unregulated and pin 2 was +16 volts while pin 52 was -16 volts, again both unregulated.

One problem of unplugging a board with power on could cause the + and - 16 volts to short together.  Murder on the traces on the motherboard.  Personal experience on that front.

Steve G./N4TTY
Sent from my iPhone

> On Dec 22, 2014, at 19:34, "drlegendre ." <drlegendre at gmail.com> wrote:
> 
> Kind of a long shot, but I can't think of anywhere better to ask..
> 
> I have here a completely un-documented serial communications board, for S-100 computers. Photos can be seen at: 
> 
> https://nerp.net/~legendre/altair/mct_serial_01.jpg
> https://nerp.net/~legendre/altair/mct_serial_02.jpg
> 
> All I know, is that it was made/sold by "MCT" - beyond that, there isn't even a model number on it, far as I can see. The few markings present seem to be for the PCB mask / artwork. 
> 
> Does anyone have experience with this board? Are there any documents available? I'd +really+ like to get it on-line so I can do something with my 8800, other than stare at the blinkenlights. 
> 
> I understand that some of the early S-100 serial boards supported both RS-232 and 20mA current-loop standards. As for this one, I'm fairly sure it's capable of RS-232 operation, but I have no idea if it's CL capable. 
> 
> But until I know how it pins-out, and most importantly, where it maps in memory, it might as well be a doorstop - and a poor one at that. 
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