exxos's Atari, Amiga & retro forum

stephen_usher wrote: 18 Feb 2025 16:15

Badwolf wrote: 18 Feb 2025 15:43 If the whole shebang were 3V3, I'd say it'd be a good way to program a board in vitro.

Except, if you look at the CPLD data sheet it almost shouts at you not to try to power the CPLD from this pin. :-) It's not directly connected to Vcc. It's a sense output only. It also says not to power it until the CPLD has been powered up first.

Which pin do you mean? On all my boards the 3V3 JTAG pin is a direct connection to board 3V3 and goes to all the normal CPLD 3V3 places.

BW

Really? From what I remember the CPLD has a programming sense pin output which is 3.3v. I may be remembering incorrectly. I'm pretty sure I read that from a data sheet. I'm starting to doubt myself now.

Can't really tell if you guys are agreeing or disagreeing on the same point, but all I can say is when I started programming Xilinx with a Pi I was warned heavily to make sure I remove the 3v3 line off the JTAG and always make sure the CPLD was powered by the voltage regulator on the PCB.

I don't know anything about how the PI hooks up..

But on all my boards, 3.3V on the JTAG connector is wired to the 3.3V power rail. It is just a voltage sense pin to let the programmer know that the PLD is powered up, because obviously, you cannot program the chip if it is powered down, hence the requirement for a voltage sense pin.. AFAIK anyway.

I guess it will probably work just as well if the sense pin went via a 10K resistor.. But I haven't looked any of this up...

Steve wrote: 19 Feb 2025 07:56 Can't really tell if you guys are agreeing or disagreeing on the same point, but all I can say is when I started programming Xilinx with a Pi I was warned heavily to make sure I remove the 3v3 line off the JTAG and always make sure the CPLD was powered by the voltage regulator on the PCB.

We both agree that if you power the board from the Pi then you've been naughty and Father Christmas won't bring you any presents.

Stephen's sure he's not going to be bring you a bike. I reckon he's not going to bring you a football.

BW.

Thanks a lot for all the suggestions and the lively discussions on how to use a Raspberry Pi to flash new firmware on the DFB1X.

One question for clarification: since it was mentioned that the 3v3 line on the connector on the DFB1X should not be connected, but the DFB1X needs to be powered on in order to be able to flash new firmware, does that mean that flashing is only possible if the DFB1X is installed in the Falcon and the Falcon itself is powered on?

don_apple wrote: 20 Feb 2025 11:13 does that mean that flashing is only possible if the DFB1X is installed in the Falcon and the Falcon itself is powered on?

That's the way I do it.

Thanks, good to know!

Hopefully I will have some time over the weekend to play around with this, to see if xc3sprog running on the Raspberry Pi can at least detect the xilinx on the DFB1X.

I would honestly just get a proper programmer... With the talks of potential damage, which I cannot verify either way, you could inadvertently end up killing something. I personally wouldn't risk it.

exxos wrote: 13 Feb 2025 15:58 EDIT:

You cannot run Flash and the motherboard ROM at the same time (other than when the DFB1X is disabled that is) because the blitter will trigger both the flash and the motherboard ROM at the same time upon access. So will end up with a bus conflict between the flash and the ROM if they are not the exact same version.

@exxos
Excuse my ignorance: Does this mean I can leave the TOS ROM in place IF they are both (flashed and physical) 4.04? I recently removed TOS ROM (and the FPU) but had been using my Falcon with the physical ROM in place without any perceivable issues. Ideally would like to do the update to v105 but unless I can find a step by step guide on how to flash I'd prefer not to risk bricking my DFB1X. Thanks!