TF536 + 68000 relocator and ROM board project.

All about the TF536 port to the ST.
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PhilC
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Re: TF536 + 68000 relocator and ROM board project.

Post by PhilC » Mon Oct 12, 2020 9:03 pm

Forgot to mention I'm using EmuTOS so I can boot from HD
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Re: TF536 + 68000 relocator and ROM board project.

Post by stephen_usher » Mon Oct 12, 2020 9:11 pm

Do you have extra power going to the TF? I do, via the relocator board. I replaced the capacitor next to the accelerator socket with a right-angled jumper and soldered the capacitor underneath.

I'm running TOS 2.06 from the (upper half) of the ROM. (And can boot from ACSI surprisingly.)
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Re: TF536 + 68000 relocator and ROM board project.

Post by stephen_usher » Mon Oct 12, 2020 9:13 pm

See the problem with trying to fit the keyboard....?
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Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.

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Re: TF536 + 68000 relocator and ROM board project.

Post by PhilC » Mon Oct 12, 2020 9:25 pm

Ok, I've been looking at track lengths etc for the lwct hand socket and having just seen the keyboard problem I've been thinking of where else things could go.

What do you tbink of this layout suggestion @stephen_usher ?
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I also noticed that the rom lines don't go to each socket in parallel but some to one and then some to the other, meaning track lengths can vary quite a bit on the address bus?
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Re: TF536 + 68000 relocator and ROM board project.

Post by derkom » Mon Oct 12, 2020 9:37 pm

PhilC wrote:
Mon Oct 12, 2020 9:25 pm
I also noticed that the rom lines don't go to each socket in parallel but some to one and then some to the other, meaning track lengths can vary quite a bit on the address bus?
8 MHz clock means a 37 meter wavelength. I really doubt track length variations are going to come into play here.

I seem to recall something about 10% of a wavelength being the place where you start to see problems, and certainly nothing on any reasonable size board is going to come close to that at 8 MHz. :)

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Re: TF536 + 68000 relocator and ROM board project.

Post by PhilC » Mon Oct 12, 2020 9:43 pm

@derkom no arguments there but just thinking the circuit should be the same between the two sockets and the 74ACT157 and that my TF536 at least, works better in the nearer socket.
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Re: TF536 + 68000 relocator and ROM board project.

Post by exxos » Mon Oct 12, 2020 10:03 pm

Lengths of tracks cause more ringing/oscillations the longer they are. Also they can couple to other tracks, such as gnd fill, which adds a few pF capacitance, and with the longer track lengths, you just built a oscillator. You have to use 2.2K bus resistors to help combat it all.
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Re: TF536 + 68000 relocator and ROM board project.

Post by stephen_usher » Mon Oct 12, 2020 10:12 pm

I've just been using the oscilloscpe. Very interesting spikes on the /RESET line. On the 68000 socket I'm getting them at 60Hz and on the Accelerator at 230Hz.

The power and ground are quite noisy too, unsurprisingly. On the Mk.II board I've been starting to design I've increased the power traces to 6mm (any more and the autorouter fails).

The address and data lines look a little bit noisy but not too bad. AS from the TF is only 3.3V so could probably do with buffering onto the TTL bus.

The CLK line looks good on both sockets.

Oh, and the floppy doesn't work properly at the moment.

Anyway, I've run out of time tonight, I'd better pack up.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.

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Re: TF536 + 68000 relocator and ROM board project.

Post by exxos » Mon Oct 12, 2020 10:16 pm

You need to use power planes for this stuff. If your just routing a power "track" its going to be nothing but headaches.

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Re: TF536 + 68000 relocator and ROM board project.

Post by stephen_usher » Mon Oct 12, 2020 10:48 pm

Hmm.. that would mean going up to a four layer board, which increases the costs hugely.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.

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