ATekGuy Posted May 20 Share Posted May 20 I'm trying to find out what this card might be. Does anyone here recognize it? Quote Link to comment Share on other sites More sharing options...
brain Posted May 20 Share Posted May 20 User port RS232 for VIC/64/128. I don't think it'll work on SX as I think it's using the 9VAC on the user port 2 Quote Link to comment Share on other sites More sharing options...
+OLD CS1 Posted May 21 Share Posted May 21 2 hours ago, brain said: User port RS232 for VIC/64/128. I don't think it'll work on SX as I think it's using the 9VAC on the user port Yup. Looks like a bridge rectifier there. Never really thought about the +/-12VDC levels of '232. Now I have to look to see if the other userport RS-232 interfaces I have use 9VAC. My cobbled together interface is all TTL and it worked just fine. 2 Quote Link to comment Share on other sites More sharing options...
ATekGuy Posted May 21 Author Share Posted May 21 (edited) Interesting! From the MSD marking, is it something Micro Systems Development put out, and if so, for something particular? Sorry for the questions, but I have a pile of old boards from someone who used to experiment with commodore in the 80s, and this one is the only I have no info on. Edited May 21 by ATekGuy Quote Link to comment Share on other sites More sharing options...
nick3092 Posted May 21 Share Posted May 21 (edited) 11 hours ago, ATekGuy said: Interesting! From the MSD marking, is it something Micro Systems Development put out, and if so, for something particular? Sorry for the questions, but I have a pile of old boards from someone who used to experiment with commodore in the 80s, and this one is the only I have no info on. Commodore never had an RS-232 compliant serial port. This board gives you one via the user port. Of course, I'm pretty sure you would still need software that was aware you had it plugged into the user port. Looks very similar to a design that was apparently published in Byte magazine a few years later. Edited May 21 by nick3092 1 Quote Link to comment Share on other sites More sharing options...
ATekGuy Posted May 21 Author Share Posted May 21 Wow, that is very similar! Quote Link to comment Share on other sites More sharing options...
+OLD CS1 Posted May 22 Share Posted May 22 7 hours ago, nick3092 said: Commodore never had an RS-232 compliant serial port. This board gives you one via the user port. Of course, I'm pretty sure you would still need software that was aware you had it plugged into the user port. Looks very similar to a design that was apparently published in Byte magazine a few years later. I am unsure of where I found the circuit I used, but it did not use any fancy 1488/1489 RS-232 transceivers, just a few transistors. When I think about it, I bet I was over-driving my 6526. 1 Quote Link to comment Share on other sites More sharing options...
ATekGuy Posted May 23 Author Share Posted May 23 Ok guys, I really do appreciate the technical info of the circuitry (I love learning how things were accomplished back then), but I'm also trying to know who made this. It looks commercial with that marking, but I can't find it anywhere in my research. If it's an MSD product, is there a document somewhere? 1 Quote Link to comment Share on other sites More sharing options...
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