exxos's Atari, Amiga & retro forum

OK, after more testing I think that I can say that the problem is that the writes to the device aren't happening.

For those not in the know, the trick being used to write is to put the data into one byte of the address whilst doing a read cycle. From what I understand the device then picks up the value held in the address and writes it into a location held elsewhere in the address. For whatever reason this is not working.

Can the hardware people think of possible reasons for this on some TTs but not others? Voltage loss on the address bus making it too low for the NetUSBee device to read reliably? If so then why can it access the device ROM and do reads?

I'm flummoxed.

(I've cleaned the ROM port as best I can. I've pushed the tines in so they make harder contact. I've looked at them under a magnifying glass and they all look OK.)

Looking at this a bit further: If I run ht1ene.tos test continuously it will eventually crash with "Illegal Instruction". It will do this at a random time, sometimes quite quickly, which suggests that maybe there's a poor interaction between the data bus and the RTL ethernet chip causing corrupted instruction fetch by the CPU. More evidence pointing to this is that if the CPU cache is turned off it happens more quickly.

I don't know about either thing.. But could it be a bus loading issue as I've had that problem on my ste recently..where plugging in a cart would give the impression of bad tos ROM.

As far as I know, the NetUSBee design is available to the public. So maybe someone should review the schematic. Could be (capacitive) loading of the bus, but could also be that the buffers on the NetUSBee due to some glitch in the logic design output data to the bus when they shouldn't do so.

I've downloaded the documentation but it doesn't seem to have a logical diagram, merely a set of board layouts for a certain PCB design program.

In the download I do see the schematic file: version1.sch.
However, as you mentioned, it is for the less well known design software Number One Systems EasyPC. Now, I don't have a NetUSBee and won't get invested in this. But you could try if the schematic can be opened with the demo/trial version of said program: https://www.numberone.com/. Or you could redraw the schematic from the PCB layout (provided in industry standard Gerber format) or from your actual hardware.

The software method is probably the only way given that the Lotharek board is multi-layer and has an upper paint layer obscuring all the tracks.

The schematics seems really simple and is available in the etherne.zip file in the ETHERNEC directory as SCHEMAT.GIF :
This doesn't have the USB part but the ethernet part is there.

I downloaded the demo version of the Easy PCB software (you have to register with them... little bit annoying) and I can open the sch file for the NetUSBee.
So we should be able to redo it in Eagle.

The access for the RTL8019AS is exactly the same as the original ethernec :