exxos's Atari, Amiga & retro forum

What about the reset signal....

exxos wrote: 05 Apr 2020 13:00 What about the reset signal....

Yeah, the reset signal had crossed my mind, it's not present at all on the Mega socket.

@exxos I presume it needs to held high or low?

rubber_jonnie wrote: 05 Apr 2020 13:08 @exxos I presume it needs to held high or low?

High I presume.

exxos wrote: 05 Apr 2020 13:15

rubber_jonnie wrote: 05 Apr 2020 13:08 @exxos I presume it needs to held high or low?

High I presume.

I'll see if the schematics show, but high would make sense.

Here is a small delay circuit for the reset line (about 20ms). The cap is a electrolytic capacitor.

I have checked the IKBD CPU datasheet and the reset is active low, so tried pulling it high, but no difference, I also joined the GND pins for the KBD (1 & 8) together,just in case that was an issue.

Checking the IKBD reset on a working STFM, I confirmed it's active high, and goes low when reset is pressed as expected. I tried switching the TX/RX lines, these are the combinations of hookup I've tried:


And I have also tried with reset open and tied to GND and pin 1 not connected at all. Keyboard is working fine on another STFM.

I suppose it is possible that connecting an STFM keyboard to a Mega ST just isn't possible, though it seems odd that it can be done the other way around. More research needed.

DoG wrote: 05 Apr 2020 15:45 Here is a small delay circuit for the reset line (about 20ms). The cap is a electrolytic capacitor. hw-rj12 electrolytic capacitor.jpg

@DoG Thanks I'll give that a go. I was wondering if some sort of delay might be needed. TBH I haven't checked reset with a scope,only a logic probe up to this point.

Not progressing with this due to other things, plus a load of info on AF is temporarily unavailable. Parking for now, but I'll be back :)

When googleing about this some time ago I found someone have done it but I think he used other values on the cap and resistor to get it working. I'll try and find the post again. But I bet you it was on Atari-Forum and that's down at the moment.

rubber_jonnie wrote: 23 May 2020 10:29 Not progressing with this due to other things, plus a load of info on AF is temporarily unavailable. Parking for now, but I'll be back :)

Did you get this working in the end?