Cartridge Port: Would a buffer board help with problems?

[DoG]

I'm wondering how feasible it would be to add pull-up resistors into the address lines on the cartridge. I've no way of making a PCB with a male edge connector and female edge connector.

Could this work for you: https://www.ebay.com/itm/NEW-Atari-ST-c ... 3395781860

You should be able to add your resistors on that board.

EDIT: Sorry, it didn't have the female connector on it. No thru port.

[stephen_usher]

I'm wondering how feasible it would be to add pull-up resistors into the address lines on the cartridge. I've no way of making a PCB with a male edge connector and female edge connector.

Could this work for you: https://www.ebay.com/itm/NEW-Atari-ST-c ... 3395781860

You should be able to add your resistors on that board.

EDIT: Sorry, it didn't have the female connector on it. No thru port.

Indeed, which is a pity.

[exxos]

Bad address and databus etc is the route of most of my troubles..What you see is "normal" for the ST. Its a wonder the things ever booted or worked from day 1.

Like I said earlier, my diagnostic board wouldn't boot with "Finger on board", so the resistance of my fingers was enough to cause the machine not to boot up... So even down to tollertances on the carts , one cart may work, and another may not.

So I could try and hack on some pullups on the cart and see what happens.. use 4.7K's .... Any sort of loading on the cartridge port will "overload" the 10K pullups normally on the machines... I think on the STE they changed the address pull ups to 4.7K in later revisions.

[stephen_usher]

OK, I put some 4.7K pull-ups on the NetUSBee and...

IMG_1500.jpg

Still shark fins. It looks like something has a massive capacitance somewhere.

[exxos]

That's about as good as things get.. But does it help ?

[stephen_usher]

That's about as good as things get.. But does it help ?

Nope.

I'm guessing that the slow rise is causing a timing problem, with the address being read from the bus before the voltage has reached the 'high' level. Maybe the old power supply produced a slightly higher voltage which would mean that the curve would be steeper and hence go above the TTL high level earlier.

[exxos]

You could try 2.2K instead. Though when it starts getting into these screwy problems.. its why I gave up working on Falcon and STE stuff as the problems never seem to end. Very hard to debug someone else's designs ontop of it all as well.

[stephen_usher]

I've just tried on the TT.... It helps a bit. More of the NetUSBee operates and it passes the tests, though doesn't actually send packets.

As for changing the value of the resistors, I'll have to get some more resistors. As it was I had to use a mix of 4.7K and 5.3K(?) as I only had sets of ten resistors of each type in the box I bought a long time ago.

P.S. Putting a 'scope on the TT address bus that actually looks really nice and clean, though there's a different form to the signal, in that it's a long high followed by a very short low, followed by a short high and then it goes low until the next cycle. I wonder if that's what confuses the NetUSBee and the Spectre GCR.

[exxos]

2.2k sils maybe the way to go. Though its possible you may need to change all the pull ups on the address and databus.