Ethernet for the QL

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Peter
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Re: Ethernet for the QL

Postby Peter » Fri Feb 19, 2021 2:04 pm

Hi Dave,
Dave wrote:I do like the idea of a Q68 compatible Ethernet card.

Would you mainly target (S)GC or QL? (S)GC is always a mechanical difficulty, when one needs decent write access to registers and can therefore not abuse the ROM port.

Dave wrote:Could the VSYNC signal be used as a fast timer?

Yes, but the code changes to go without hardware timer are small. More important to deal with the IRQ issue.

All the best
Peter


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Dave
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Re: Ethernet for the QL

Postby Dave » Sat Feb 20, 2021 9:28 pm

An ethernet card with a thru-connector for the SGC and 100% pass-thru should work?

I don't know what the special IRQ handling requirement is.

I have all the parts here to assemble 10. I have a hundred CP2200 and 10 magnetics/sockets. I also have 20MHz xtal.

I just have crippling ADHD and have a really hard time finishing anything - I'd have to be constantly reminded and encouraged and that is a lot to ask of anyone. It's a shame, because I can sit and layout and assemble all day and love it. I just.... ooh, shiny.


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Peter
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Re: Ethernet for the QL

Postby Peter » Sat Feb 20, 2021 9:59 pm

Dave wrote:An ethernet card with a thru-connector for the SGC and 100% pass-thru should work?

Yes, but how to lead out the network socket? (Also see the earlier discussion.)

Dave wrote:I don't know what the special IRQ handling requirement is.

Unfortunately the CP2200 activates the IRQ line when it powers up. A simple register write can disable interrupts, but that would mean to change the OS. So you'd need to add a little extra logic to gate off the IRQ line until needed. (Also see the earlier discussion.)

Dave wrote:I have all the parts here to assemble 10. I have a hundred CP2200 and 10 magnetics/sockets. I also have 20MHz xtal.

That's cool. The CP2200 is not recommended for new designs anymore, so maybe the chips will become valuable. I was already considering to get some stock myself, but will wait until it's last-time-buy. Please don't sell them elsewhere before asking me.


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Re: Ethernet for the QL

Postby Dave » Sat Feb 20, 2021 10:25 pm

Peter wrote:
Dave wrote:An ethernet card with a thru-connector for the SGC and 100% pass-thru should work?

Yes, but how to lead out the network socket? (Also see the earlier discussion.)

For maximum flexibility, I think the card would have to be BBQL friendly with some RAM onboard. If it were half eurocard sized anyway, it could have three backplane slots on it. That would work in every system? Looking at the magnetics, they would juuust fit under the lip of the case at the back, which is nice.

Peter wrote:
Dave wrote:I don't know what the special IRQ handling requirement is.

Unfortunately the CP2200 activates the IRQ line when it powers up. A simple register write can disable interrupts, but that would mean to change the OS. So you'd need to add a little extra logic to gate off the IRQ line until needed. (Also see the earlier discussion.)

I'd naturally use a GAL for address decoding anyway - likely an ATF1502. Looking at an existing design I have (4/8MB SRAM card) which already uses an ATF1502, it has a bunch of free pins.

Peter wrote:
Dave wrote:I have all the parts here to assemble 10. I have a hundred CP2200 and 10 magnetics/sockets. I also have 20MHz xtal.

That's cool. The CP2200 is not recommended for new designs anymore, so maybe the chips will become valuable. I was already considering to get some stock myself, but will wait until it's last-time-buy. Please don't sell them elsewhere before asking me.

I offered them to Derek for Q68, but he had another source. You guys will always get first refusal.


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Re: Ethernet for the QL

Postby Dave » Sat Feb 20, 2021 10:39 pm

Dave wrote:
Peter wrote:The CP2200 is not recommended for new designs anymore, so maybe the chips will become valuable. I was already considering to get some stock myself, but will wait until it's last-time-buy. Please don't sell them elsewhere before asking me.

I offered them to Derek for Q68, but he had another source. You guys will always get first refusal.

I don't think access to parts is a problem. Internal pricing is half retail.

IMG_2338.jpeg


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Peter
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Re: Ethernet for the QL

Postby Peter » Mon Feb 22, 2021 9:22 pm

Hehe, nice one! And please give us a shout if you get insider info that the CP2200 is close to last-time-buy. ;)


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Re: Ethernet for the QL

Postby Peter » Mon Feb 22, 2021 9:36 pm

Dave wrote:For maximum flexibility, I think the card would have to be BBQL friendly with some RAM onboard.

I think that would be a nice combination. It appears that rates of 40 KBytes/s are doable even with the 68008, so together with a QL-SD interface it would make a nice retro system. I have found ethernet file exchange with a PC very helpful - the back and forth with SD cards tends toward data corruption for me, as I sometimes forget to unmount on the PC side.


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Re: Ethernet for the QL

Postby Dave » Tue Feb 23, 2021 4:54 pm

My instinct here would be to use an ATF1502 as decoder and IRQ hold. It has the capacity to do all address decoding for chip selects for RAM and ethernet, a single flipflop to hold interrupts until they're enabled. If reconfiguring the CP2200 is a single write cycle, it could be triggered by /WR and /CSE going from low to high, or some other recommended scheme.

A programming port would be included, so the device could easily be updated. RAM would need to be optional, as there's systems where it wouldn't play nice, and systems where it wouldn't provide any benefit.

I'm going to make a polite suggestion/request at this point. I have a long history of not finishing things. I have crippling ADHD. If you gently and consistently ask me about it or raise it in my awareness, it will stay front and center.


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Re: Ethernet for the QL

Postby Derek_Stewart » Tue Feb 23, 2021 5:16 pm

Dave wrote:I offered them to Derek for Q68, but he had another source. You guys will always get first refusal.

I can not remember this, maybe I forget...


Regards,

Derek
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Peter
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Re: Ethernet for the QL

Postby Peter » Thu Feb 25, 2021 9:56 am

Dave wrote:I'm going to make a polite suggestion/request at this point. I have a long history of not finishing things. I have crippling ADHD. If you gently and consistently ask me about it or raise it in my awareness, it will stay front and center.

Although for a different controller, we see encouraging ethernet figures for a RAM expanded QL without (S)GC here:
https://qlforum.co.uk/viewtopic.php?f=2&t=330&start=30#p39849
So I think a straightforward RAM expansion with CP2200 ethernet would be something that can be finished, and also offers good value.
Not every retro QLer can/will get a (S)GC, but almost everybody needs RAM expansion, e.g. to decently use QL-SD.
So if that RAM expansion comes with an extra goodie, but not much higher costs, I'm sure it will sell well. I'd definitely buy one.

You already have existing circuitry for both the CP2200 and RAM. That's a good starting point. To reduce risk of not finishing the card, you could omit optimizing it for (S)GC.



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