On 2016-Feb-07, at 6:17 AM, Robo58 wrote: > c). I hand assembled some code to exercise the 6850. I know it has a > software reset and then you set attributes. I tried my buddies echo > program. It looks for a received character and then echo's it. I'm using a > laptop and PuTTy along with an RS-232 breakout box. I can see characters > going in but nothing coming out. The 6850 appears to drive the bus for a > finite amount of time and then turn off its drivers. I don't have any > experience with the part and I don't know if that's the way it's supposed to > work or that the Altair has a bus timing issue.
How about doing a program that simply repeatedly outputs a character first, getting that going before trying to deal with input - cuts the problem space in half. The repeat loop should give you some consistent bus activity and observable waveforms on a scope if you have one, rather than trying to catch events initiated from external input activity.
