BLITTER RE-CREATION THOUGHTS

Progress on our FPGA cores.
czietz
Posts: 548
Joined: Sun Jan 14, 2018 1:02 pm

Re: BLITTER RE-CREATION THOUGHTS

Post by czietz »

exxos wrote: Sat Dec 22, 2018 10:39 am But 3 different chips from 3 different manufactures all doing all manner of various crazy.. Obviously I am doing something wrong or killing them somehow.
I assume you already checked trivial things, such as accidentally assuming a wrong pin-out? I have used MOSFET switches in the past (would need to look up the part number, though) and I didn't find them "temperamental".
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: BLITTER RE-CREATION THOUGHTS

Post by exxos »

I've worked from the data sheets in all cases.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: BLITTER RE-CREATION THOUGHTS

Post by exxos »

So single mosfets isn't going to be pretty...

22.jpg
22.jpg (154.55 KiB) Viewed 5387 times

So I have found a dual mosfet in a slightly smaller package and some SMT resistor networks to keep sizes down...

Will see how that layout goes later....


EDIT:

Its a lot smaller and that could work..

23.jpg
23.jpg (115.64 KiB) Viewed 5376 times
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: BLITTER RE-CREATION THOUGHTS

Post by exxos »

I got sidetracked looking for IC's once again..

I found a NXP part GTL2003 so ordered one yesterday and arrived today.. and this one works!!


3.3V as expected on the "left side" of the chip..

IMG_3723.JPG
IMG_3723.JPG (139.89 KiB) Viewed 5322 times

5V on the right side of the chip..

IMG_3724.JPG
IMG_3724.JPG (142.08 KiB) Viewed 5322 times


If either side goes low, the other side goes low as well.

IMG_3725.JPG
IMG_3725.JPG (124.18 KiB) Viewed 5322 times

So it's very possible I will be able to use this part instead of single mosfets :D :D


EDIT:

Interestingly, The 3.3V side doesn't seem to actually need a pull up resistor, and it still outputs 3.3V... So I need to look into that more, but that would save needing all the pull up resistors!


EDIT2:

1.jpg
1.jpg (103.28 KiB) Viewed 5308 times
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
ijor
Posts: 428
Joined: Fri Nov 30, 2018 8:45 pm

Re: BLITTER RE-CREATION THOUGHTS

Post by ijor »

exxos wrote: Fri Dec 28, 2018 3:21 pmI found a NXP part GTL2003 so ordered one yesterday and arrived today.. and this one works!!
Great!
Interestingly, The 3.3V side doesn't seem to actually need a pull up resistor, and it still outputs 3.3V... So I need to look into that more, but that would save needing all the pull up resistors!
I don't think you necessarily need pull ups on either side. This is how this type of switches works. You only might need pull ups on the high voltage side (5v), and only if you want a full voltage swing. Without pull ups it would work, but it would never reach 5v.

However, for most if not all of these signals you already have 5V pull ups on the motherboard. Most pull ups are not too strong, you know better than me, they are designed just to avoid the signal ever be floating. You might replace them for stronger pull ups. But if you consider this important, IMHO you should better use a transceiver that actively drives all the way to 5V.
http://github.com/ijor/fx68k 68000 cycle exact FPGA core
FX CAST Cycle Accurate Atari ST core
http://pasti.fxatari.com
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: BLITTER RE-CREATION THOUGHTS

Post by exxos »

ijor wrote: Sat Dec 29, 2018 12:04 pm However, for most if not all of these signals you already have 5V pull ups on the motherboard. Most pull ups are not too strong, you know better than me, they are designed just to avoid the signal ever be floating. You might replace them for stronger pull ups. But if you consider this important, IMHO you should better use a transceiver that actively drives all the way to 5V.
It does drive to 5V. Though that is done on the motherboard pull-ups anyway. The 3.3V side doesn't need the pull-ups, so I hope I can tweak my original IDT layout to use the NXP chips without much fuss.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: BLITTER RE-CREATION THOUGHTS

Post by exxos »

I've been looking at the GTL2003 chip footprint (TSSOP20) , and with my current PCB design its just not going to fit :( Because they are 8bit devices, 2 are needed each side of the FPGA... there is only just enough room for the 16bit chip..

I have been talking to Icky about this earlier today as well. How it looks, it will have to have the FPGA "above" the blitter socket.. but this does mean the board will be solder in , not "plug in". Its not going to fit all machines, but compromises & choices have to be made and that looks like the only way forward now.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
Icky
Site Admin
Site Admin
Posts: 3986
Joined: Sun Sep 03, 2017 10:57 am
Location: UK

Re: BLITTER RE-CREATION THOUGHTS

Post by Icky »

As mentioned by Exxos, we have been discussing the fit of these Blitter boards.

It should fit both orientations of the bottom right Blitter socket location on most ST motherboards and miss the shielding but we won't fully know until we get one of these built.

Of course this version will not fit motherboards with SMT Blitter locations.

IMG_3714.jpg
IMG_3714.jpg (265.46 KiB) Viewed 4416 times
IMG_3715.jpg
IMG_3715.jpg (266.99 KiB) Viewed 4416 times

All That Glitters - Here is an image of the Blitter board. There still is a lot to do but we are making progress.

All That Glitters.jpg
All That Glitters.jpg (326.09 KiB) Viewed 4416 times
User avatar
PhilC
Moderator
Moderator
Posts: 6016
Joined: Fri Mar 23, 2018 8:22 pm

Re: BLITTER RE-CREATION THOUGHTS

Post by PhilC »

I know I've asked before but why hot choose the combined blitter,glue,mmu you have on the STE?

Is it just a matter of knowing the pin out etc? Was especially thinking this when doing the Mongrel board. One chip instead of 3 SMT ones.
If it ain't broke, test it to Destruction.
User avatar
rubber_jonnie
Site Admin
Site Admin
Posts: 10472
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: BLITTER RE-CREATION THOUGHTS

Post by rubber_jonnie »

Damn, somebody had another idea, I'm going to have to build one of these too! Takes mental note to buy a mainframe to maintain complex list of 'projects in flight'.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
Post Reply

Return to “FPGA DEVELOPMENT”