Now a question.. Can someone give me a quick rundown on how the CPU communicates with this board? Does the board show up as a few bytes in the memory map, like on page zero? Does it connect directly to some registers in the CPU? How does data move from the CPU / buss into & out of the board?
In short, how does the computer know where to "find" the board - and how do they converse? I'm only concerend with the serial portion, the rest is still a mystery - the 50 pin headers might be anything from parallel ports to (proprietary?) controller interfaces. On Thu, Oct 1, 2015 at 6:21 PM, drlegendre . <drlegen...@gmail.com> wrote: > @Chris > > That's an intriguing and very real possibility, but then there's this: > http://www.mct.net/ - Does that logo look familiar? Founded in the 80s, > controller boards, interface modules, single-board computers.. but yes, > they are in Germany. I did try contacting them, but never heard back. > > @All > > To answer a few questions: > > Yes, I am certain this is an S-100 board. It was pulled from the Altair I > rebuilt and the PO confirmed that he "had a terminal or something" > connected to it. > > The burned area on the board is where a couple of zener regulators gave it > up. You can maybe see that I've replaced them with 3W zeners and 1W > resistors. I believe these create +/- 12V supplies for the op-amps and > RS-232 levels? > > I did some tracing on it, not my cup of tea, but I did learn some things.. > here's what I found: Each of the two 10-pin headers (I'll call these serial > ports) seem to be wired the same, with duplicate component setups for each > port. > > Pins 4 & 6 connect via 175R and 47R resistors, respectively, to one input > of an XNOR gate on an LS266 chip. Second input to same XNOR gate seems tied > to Vcc via jumpers. Output of XNOR gate has 1K pull-up to Vcc (open > collector output) and then connects to pin 20 on the 1014/15 UART which is > "SI". So pins 4 & 6 seem to be our serial inputs (RxD) with two different > series resistances offered (175R or 47R). Might be an input voltage divider > or termination option? > > Pin 1 connects to the collector of a 2N3906 which is in turn driven by the > output of one section of an LM1458 op-amp. The non-inverting input of the > op-amp connects back to pin 25 on the UART, which is "SO". I'm not sure > what the inverting input of the op-amp is tied to.. perhaps it's part of an > enable circuit? But it seems pin 1 is our serial output (TxD). > > The other port pins are variously tied to resistors, jumpers and/or 74XX > logic. These might be our handshaking lines, ring detect, etc. > > That's all I know so far. > > On Thu, Oct 1, 2015 at 3:30 PM, Chris Elmquist <chr...@pobox.com> wrote: > >> I've got another theory regarding drlegendre's board. >> >> I happen to know via out-of-band information that he is here in MN. >> >> There is a company in the Twin Cities called Micro Component Technology >> that existed in the 70s, 80s, 90s and still today. >> >> They make handling and test systems for IC fabrication. >> >> http://www.mct.com/Company.aspx >> >> I'm willing to bet dollars to donuts or lingonberries to lefse that his >> board is a custom job made by the MN MCT and it went into the computer >> control of one of their machines from the early 80s. Something probably >> designed in the mid to late 70s. >> >> The logo on the board matches what I remember seeing on their building >> in Shoreview ages ago. >> >> I don't think it's the MCT that made PC (as in IBM PC) plugins... >> >> Chris >> >> >> On Thursday (10/01/2015 at 10:14AM -0500), Jay Jaeger wrote: >> > I had a look, and it seems to me that there is more going on on this >> > board than just serial ports. It is even possible that the system it >> > was in had essentially re-purposed the board to use for a serial ports >> > in a way that the original designer did not intend. That would explain >> > the lack of obvious level shifting - it may have been used for TTL level >> > serial I/O. >> > >> > Also, there are lots more passive components on this board than I would >> > expect for a serial interface board. >> > >> > A company with these initials made EPROM programmers, though their logo >> > was different - but perhaps it changed over time. Maybe this was a very >> > early interface board to one of their very early programmers - and >> > perhaps it is missing some of the parts, like connector headers and >> > resistor packs, and then was re-purposed. >> > >> > JRJ >> > >> > On 9/30/2015 7:52 PM, drlegendre . wrote: >> > > (Months along, posts to several boards / lists, still no help on this >> one.. >> > > so I'm giving it another shot. I'd really like to use this board) >> > > >> > > Been trying to no avail to find any info on this 'MCT' S-100 serial >> card. >> > > I'm pretty sure the card works, as it came from a previously-working >> system >> > > - but all documents are missing, and without the info, I have no idea >> how >> > > to put it to use. Photos are here: >> > > >> > > https://nerp.net/~legendre/altair/mct_serial_01.jpg >> > > https://nerp.net/~legendre/altair/mct_serial_02.jpg >> > > >> > > Other than what I believe is an artwork / batch number on the rear, >> the >> > > only marking is "Assy 105510" on the front silk screen. My hunch is >> that >> > > this may have been a fairly generic 'OEM' type card which could have >> been >> > > re-badged and sold under one or more different names. So perhaps the >> docs >> > > exist under a name other than MCT? >> > > >> > > Any help greatly appreciated - thanks! >> > > >> > > -Bill >> > > >> >> -- >> Chris Elmquist >> >> >
