Amiga 600 schematics nearly put into Kicad

[kipper2k]

Originally Posted by Mick

If you list the exact signals I will as they won't really impact anything but I don't want to clutter it with all kinds of mods for now, I'm going to release the files so people will be able to mod it until their heart is content.

Actually, one thing I wondered about kipper is what are you using for the A500 keyboard controller on your MX keyboards and could it be used in the A600? the reason I am asking is I've looked around for the A600 keyboard chip and they are nowhere to be found.

Hi Mick,

We are using the PIC18f45K50. it would probably be very difficult to integrate it onto the motherboard. i will think and ask some questions on this and see if there is a solution for you. I think with the motherboard rebuild projects it is difficult to find the chips (and sometimes being held hostage to peoples prices).

as for the CPU signals... in order to make some sort of accelerator that doesn't require to sit on a PLCC socket all the signals need to be transposed. This way a small board can be used to provide signals to yet unmade cards

[Mick]

Do you have a particular location in mind or can I just squeeze it in close to the CPU? orientation?

[kipper2k]

Originally Posted by Mick

Do you have a particular location in mind or can I just squeeze it in close to the CPU? orientation?

the best location is somethere that wont interfere with other peoples addons...

I am thinking somewhere that doesnt require long cables, mabbe just above the expansion slot. That way something could sit in the slot and also have mating headers to access the CPU signals also

[Mick]

Can it be to the right of Gayle adjacent with an expansion card slot or do you want it closer to the top for things other than expansion cards? I'm just thinking about routing it's totally empty signal wise at the bottom of the board. I was probably going to try autorouting it with 4 layers anyway but if it fails someone else will probably have route it.

[kipper2k]

Originally Posted by Mick

Can it be to the right of Gayle adjacent with an expansion card slot or do you want it closer to the top for things other than expansion cards? I'm just thinking about routing it's totally empty signal wise at the bottom of the board. I was probably going to try autorouting it with 4 layers anyway but if it fails someone else will probably have route it.

That would be fine Mick, i am not sure where you are going to go to get the board fabricated but JLCPCB is where i use, they are fast, cheap and their boards are accurate.

if you go to 4 layers then you will be allowed smaller traces (3.5mills), smaller gaps (5mills), and smaller vias (8mills) which will help you tremendously.

When i say mills i mean thousands of an inch. I like to try to maintain 0.006" minimum trace width and 0.009" gep between traces wherever possible

here is a link to their capabilities...

https://jlcpcb.com/capabilities/Capabilities

[Mick]

I'm trying to take it one step at a time but thanks for the info, I'll be sure to look into them when I get to that stage.

Is Molex 5027906491 a suitable connector? or do you know of a better one? I'll have to make a footprint so I'd better check. Will there be any problems with keyboard clearance? I wish I had held onto the faulty board I got off Ebay but I gave it to someone for parts.

[kipper2k]

i think that is the wrong size. you need a 1.25mm connector, vertical. 31 pin. For my keyboards i am using a 32 pin header on the MX, with a 32 pin FFC cable (1mm, common as muck to buy in the event of ripping etc) and i made a custom plug that the ffc cable connects to and that plug will connect to the motherboard connector. the one i use is a right angle connector and will not fit into the motherboard so it is no good for you.

I have seen someone recently selling replacement 31 pin connectors for the Amiga, cant remember where. Try to track him down

i will confirm width of the amiga cable, i think i gave you wrong value there

[Mick]

So you mean the same kind of connector as A1200 uses for its keyboard? Molex 39532315? and fit two of them? I could just make another edge connector with all cpu signals couldn't I? wouldn't that be neater?

edit: I just realised another edge connector might block existing expansion cards. doh

[kipper2k]

Originally Posted by Mick

So you mean the same kind of connector as A1200 uses for its keyboard? Molex 39532315? and fit two of them? I could just make another edge connector with all cpu signals couldn't I? wouldn't that be neater?

Yah,

https://www.molex.com/molex/products...cts&Lang=en-US

that looks like the replacement for the original keyboard header.

the headers i am thinking about for the CPU signals is these...

https://www.ebay.ca/itm/FFC-FPC-Conn...EAAOSwPe1UFR34
2 required (the Amiga keyboard ribbon will not fit a 1mm ffc header

I like these headers as they are plentiful and cheap

[Mick]

Most of the sellers are Hong Kong and China and don't list a brand/model. Won't they have different types of footprints? I'd rather use something from Digikey/Mouser if I can? I know the pin pitch will be the same but the ends that give strength might not be? or am I wrong?

[Mick]

What are the female connectors the A600 uses for expansion cards and are they available in bigger sizes? I'm wondering if I could extend the existing connector with a lip so that it doesn't block existing cards?

[kipper2k]

Originally Posted by Mick

Most of the sellers are Hong Kong and China and don't list a brand/model. Won't they have different types of footprints? I'd rather use something from Digikey/Mouser if I can? I know the pin pitch will be the same but the ends that give strength might not be? or am I wrong?

You can log into digikey, find it and then download from "Ultra Librarian" if available or create your own footprint, it isn't that hard (at least not in Eagle). as long as you know the pitch you are pretty well set

[Mick]

I've just about found every flaw in extending the expansion connector but two ribbon connectors seems a bit messy so I'll probably leave it to others and soldier on with a basic version for now. Sorry Kipper.

Was there ever any A600 expansions other than 1MB memory? if not wouldn't it be better to try to integrate the extra 1MB and a clockport to the mainboard and then replace the signals to the expansion port with the CPU signals?

[Daedalus]

The Indivision ECS attaches to a trapdoor RAM expansion. There's no electrical reason you couldn't also add the required socket to the motherboard, but the sort of space needed means significant relayout of parts of the board, so might be another thing for a future update.

[katarakt]

Mick, do i understand this correctly you put the CXA1645 onboard to get rid of the Z things and put the s-video on the HF modulator place? Like parts from deadalus's kit and schematics from Tbtorro's CXA1645 all onboard ? This would be great

If VGA possible on this place like chuckie's reamiga this would be great too, but where to place the S-Video if VGA will be on the modulator place

Oh sure, bootselector is a must too...like on chuckies reamiga

Great work overall, A600 is the missing peace for all. I hope this will be finished

[Mick]

Hi katarakt, I don't really want to add loads of mods myself, the main plan was just to get a near bog standard replica released and people can go their own ways with it when I release the files. I'm a bit of a minimalist myself (and like to do things my own way ) but I needed to add the CXA2075M or the PCB's were only useful for transplants since the Zxxx parts are non existant and from what I've heard it's an upgrade anyway.

This is where I saw about the newer DAC:
https://www.ikod.se/cxa2075m/

It's explained in a simple way for non electrical people like me.

For the VGA I was thinking just to add a pin header and people can use a cable like with Indivision, same with s-video just a header. I'm not very good with electrical circuits though, most of what I've done is just copying schematics and then arranging parts. I'm very methodical.

[Stedy]

@Mick,

To help me with the schematics check, did you use the V1.5 or V2 as your original?

You do realise that the CXA2075 does not give you VGA compatible video timings?
It will give you Y/C (S-video), RGB and composite but all with PAL or NTSC video timings.

I can see how to remove the Keyboard interface, if you want yo only use a PS/2 PC keyboard, just hook into the _KB_DATA and _KB_CLOCK signals at the U7 (ODD) 8520 VIA.

Off to check some more.

[Mick]

I used V2 schematics.

Doesn't it support the 15khz VGA thing that everybody is doing? it doesn't matter then what about s-video? will it needs lots of extra resistors and things? if so it doesn't matter I'll leave it as it is and people can add anything they want later. I'm sure someone will make a "bells and whistles" version with all of the things people want.

[katarakt]

Maybe better leave it as it is and hopefully someone do a change. The CXA1645 is a compatible proofed working concept, so probably i wouldn't use something different and all information (layout) is available. So it should be easy for someone to do the changes.

[Mick]

I've spent most of the day routing power since there are varying track widths, could anyone explain the AGND (analogue ground?) to me please? is it connected to a separate ground plane to the rest of the motherboard? should I isolate it from the rest of the ground plane? or is it all just connected to the normal ground but close to the RCA's?

Also what board manufacturers do people recommend, I had a look at the one Kipper posted but they only do 30x30cm on more than 2 layers?