exxos blog - random goings on

[exxos]

I have been doing some more changes to the H2..

Firstly the MMU,GLUE,BLITTER,CPU have been aligned properly to a standard 2.54mm grid.. This will ultimately make things easier when designing the FPGA board.. the plan is that the FPGA board will plug into those chips directly and replace them.. Of course we only just started with the FPGA, so that idea is a long way off yet, but I started to make preparations now the future...

Also as highlighted below is the jumper/header which allows tapping into the clock lines a lot easier. So whereas on the alpha we had lots of wires everywhere when doing the 16MHz mods, on the H2 everything is rooted to that header strip... More information on that can be found here ..https://www.exxosforum.co.uk/forum/viewt ... =73&t=2011

So a stock machine is when those headers are jumper links, and when the links are removed, a future 16MHz mod board can be plugged into that connector making things ultra simple to do... And when ultimately the FPGA board is done, it will also plug into that connector and replace the clocks with the FPGA generated ones. so there should not be lots of track cutting and wires when we start accelerating the board more.

Next up I added a new 68K "expansion socket" dedicated for flashy clock. There was room at the front of the motherboard for this to fit into place so it worked out well. The problem with flashy clock is that it is designed to have the CPU on board, whereas on the remake board, the CPU is already on the motherboard.

As the next version of flashy clock will/should Automatically load settings from the NVRAM on power up, we basically had to add a couple of jumpers under the board (on the remake) to get around the CPU issue.

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Also tidied up the schematic a bit as it was getting a bit messy :lol: will post a updated schematic another time...

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[exxos]

Something else I had just "un-forgot"..

Drive AB swap jumpers...

The grey lines inside the switch represent the default (stock) setting.

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Incidentally...

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DRIVE1 & DRIVE0 are both connected on the external floppy connector.. This means the external drive can be configured as internal or external and it will still work... I think this cause some confusion in another thread a while back..

I actually think we could do this on the internal one as well, so we just don't have to bother changing the jumpers on the floppy drive itself any more...

[exxos]

OK now I am confused...


https://old.pinouts.ru/HD/InternalDisk_pinout.shtml

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On the STFM (and remake)

Pin 16 is MOTOR ON, PIN10 DRIVE SELECT...

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But on the website pinouts, pin 10 and 16 is motor on, so there is no drive A or B select on the internal ST floppy connector (pin 12 & 14) ?!


EDIT:

On the Falcon it labels drive zero and drive one, but on pins 10 & 12, not 12 & 14..

But if the pinout is different on the motherboard side, how does this even work with normal floppy drives which are a standard pinout ?!

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If the original Atari drive did have a different pinout, that would make sense, but then PC drives would surely not work then as the pinout would be wrong ?!

[DoG]

It's Shugart interface. So just scroll down a bit ;)

[exxos]

It's Shugart interface. So just scroll down a bit ;)

ah :) :lol:

So really I could just wire 10,12,14 together.

[exxos]

I have wired them together on the remake board, hopefully they'll be no more messing around with the floppy PCB changing the links over now..

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I am tempted in fixing the motor on signals, because both internal and external motors come on at the same time which is a bit rubbish... But it would likely require another chip or something :roll:

EDIT:

I guess that would actually cause a problem when copying from drive A to B as the motor would have to power up before the access happened :roll:

[exxos]

Can'ya tell what it is yet...

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[PhilC]

Is it a GAL in disguise?

Floppy controller thingy? lol?

[exxos]

Is it a GAL in disguise?

Floppy controller thingy? lol?

Close enough :)

[exxos]

It grew a little bit :lol:

I have been juggling pins around, and also routed the AB select switch via the GAL. Actually had to do this as a multiplexer, which I have not done before, so no idea if it will work or not, but either way, the AB swap can still be done via normal jumper links anyway.

The idea is that the single jumper can be used to swap DRIVE0 DRIVE1 select lines around. ultimately this could be done via a register in NVRAM somewhere. So it could be done software not hardware ultimately.


Its basically the HD7 kit integrated onto the remake board .

So I can use 1.44 floppies... Nobody else will probably be bothered, but I am :lol: But there is no need to fit this GAL anyway.. In fact, the whole circuit can just be left out anyway.

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