i8355 from SDK-85 flakey

It was Allison who said it used the SID and SOD pins of the 8085. However this agrees wit hthe schematic in the book I have. I can't find the links that Allison mentioned to seleect TTL/current loop/RS232 mode. So either there are 2 versions of the board or my scheamtics are 'simplified'. The only lionk I can see selects whether SID comes from the current loop interface or is held low. If I am reading the monitor lisitng correctly, then the bit of code starting at 0x0049 checks to see if the SID pin is high or low. If the former it assumes a working current loop device is connected (idle state would be to have the Tx loop complete. so Q1 would be turned on, so SID high) and runs the teletype monitor, if the latter, it runs the keypad/7-seg display monitor. It's possible I've totally mis-uderstood this, I am not really a programmer, and I've only just started looking at the SDK-85 monitor source listings. I suspect you could use the current loop output trransistor as this inverter (see my previous message). And I suspect that if you buffered the RS232 output from you PC (using, say, a 1489), and fed that into the current loop input -- pin 12 of J7 -- and cut R1 :-) then that would work too. Or invert the output of the 1489 (say using a '04 -- or even another secion of the 1489 as a kludge :-)) and feed it into the SID pin of the 8085 with the link S25 totally removed. I would think that 110 bard would be trivial to do, and for the amount of data you need to transfer, not a real problem. The monitor is 2K, 110 bard is 10 characters/second, so that's just oaver 200 seconds. Under 4 minutes. Or you could run the tty monitor and use the 'D' command to dump the approrpatie area of memory (0 to 7FF I think). Capture the incoming data on the PC (I think any reasonable terminal progam can do that -- C-Kermit certainly can) and write a simple program to decode the hex dump back to binary. -tony