My New Acorn Atom :)

discussion of games, software, hardware & emulators relating to the Acorn Atom
waltermixxx
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My New Acorn Atom :)

Post by waltermixxx » Tue Jan 02, 2018 10:43 pm

So my atom arrived (Thanks again, Roland!!! :0) ), and it seems to work, but it was definitely jostled on its month long trip to me. A few loose chips, and a couple that jumped out of their sockets... easy fix. :)

here she is in all her glory:
Atom.jpg
IMG_1160.JPG


I have installed AtoMMC interface (thanks Charlie) and SD card and that appears to work, i can load and save programs to the 2gig sd card. (but the *menu generates an error.) I will worry about that part later... :)

This same sd card works fine on the ZX-UNO FPGA Atom and on the real Atom... On the ZX-Uno I typed in and saved a memory test program I found in the Atom forum. It indicates RAM or ROM. I can load it from the ATOMMC on the real atom and it runs...

This acorn has 8 k of video ram #8000-9FFF, and 7k of program space. The memory test program indicates the following.
IMG_1147.JPG
IMG_1149.JPG
Any assistance appreciated. i can say the IC6 socket for the 74LS138 is rather dodgy, i put a wire wrap socket in it, and the LS138 in the socket... but still get the same memory mapping indicated above... ( when you click the image, it will rotate the right way around.) The picture of the motherboard shows the two 2114 piggy backed as well. :) with the enables tied to pin 7 of the 74LS138.

Just wondering if ram should be from #0000- and up continuous?

I am hoping to get a ram/rom board for this Atom, but have not heard back from Prime (who must be pretty busy this Holiday Season, (future thanks Prime) on availability.

I was also thinking of a 32k dead bug on the 6502 from #0000 to #7FFF?

Just wondering. How much ram does the Menu program require? ( I think it loads at #2900 and I dont think i have ram there?). I'm in the process of reading the Atom Technical Manual which should help me a great deal.

I have a buddy with a proper desoldering station (with vac) i will replace a few more sockets on this beloved Atom. :) I'm sure it will help with stability... most of the sockets have already been replaced. :)

Cheers. :)
Last edited by waltermixxx on Wed Jan 03, 2018 2:20 pm, edited 1 time in total.

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roland
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Re: My New Acorn Atom :)

Post by roland » Wed Jan 03, 2018 8:47 am

It looks like the RAM at #2C00 - #2FFF is failing. That will cause the menu program to fail. The rest of the memory map is fine for your configuration. You could try to swap IC12/13 with IC14/15 and see if the RAM gap moves to #3000-#33FF. If so, the 2114's are faulty. Otherwise check if pin 12 of IC6 makes good contact. There should be a direct connection from this pin to the CE pins of IC12 and 13 (pin 8 ).

The Atom memory map is not continuous. You can read about it in the Technical Manual here.
256K + 6502 Inside
MAN WOMAN :shock:

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Wed Jan 03, 2018 1:54 pm

Cool,

Thank you. I will try and swap ram, and definitely replace that socket.
I am so happy with this Atom, it brings back so many memories. (At least 12k of memories...he he he). I even bought a 5"black and white tv just for the experience.

Thanks again Roland, my wife thanks you as well, as I had told her, if I ever get an Acorn Atom, it would be the last Vintage machine I would buy... ;0)

Cheers.

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Re: My New Acorn Atom :)

Post by tricky » Wed Jan 03, 2018 6:03 pm

Can't help with her issues, but your Atom is gorgeous :)

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Re: My New Acorn Atom :)

Post by waltermixxx » Thu Jan 04, 2018 6:53 pm

And it looks better now that I've got the memory sorted out.

All 15k accounted for. Thanks guys for your help. I am truly chuffed!!

I swapped the ram around after checking the connection from pin 12 of IC6 to pin 8 of IC12/13. The connection was good so a swap was required. I guess reseating them as part of the swap helped. :0).
IMG_1175.JPG
IMG_1177.JPG
IMG_1178.JPG
IMG_1179.JPG

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Re: My New Acorn Atom :)

Post by oss003 » Thu Jan 04, 2018 7:45 pm

Well done Walter,

welcome as a new Atom user ........... :)

Greetings
Kees

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Re: My New Acorn Atom :)

Post by waltermixxx » Thu Jan 04, 2018 10:37 pm

Technically an OLD Acorn Atom user.... my first one in 1982 or so. :) and I'm old.... :)

and thanks for the welcome, as it's been a very long time, I may as well be a new user. :)

Cheers.

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Re: My New Acorn Atom :)

Post by roland » Thu Jan 04, 2018 10:39 pm

I'm glad you got it working. Imagine you had to send it back for repair :lol:

As long as the main board is in good condition, any Atom can be repaired :!: We have sufficient knowledge and spare parts on this forum
256K + 6502 Inside
MAN WOMAN :shock:

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Re: My New Acorn Atom :)

Post by waltermixxx » Sun Jan 07, 2018 7:58 pm

I replaced the IC24 #A000 Rom socket with a nice machined socket,
and I replaced the IC6 74LS138 socket as well, also machined. I installed a proper RCA jack for the Composite Monochrome video output.

I also began work on my 32K ram CPU socket ram board. Because it's the first 32k of ram I figure I just have to remove any ram on the motherboard in the #0000 to 7FFF range, then just connect the following pins on my cpu daughter card :

Pin Connections:
6502 to 62256
+5 to +5
gnd to gnd
D7 to D7
D6 to D6
D5 to D5
D4 to D4
D3 to D3
D2 to D2
D1 to D1
D0 to D0
A0 to A0
A1 to A1
A2 to A2
A3 to A3
A4 to A4
A5 to A5
A6 to A6
A7 to A7
A8 to A8
A9 to A9
A10 to A10
A11 to A11
A12 to A12
A13 to A13
A14 to A14
A15 to /CS
R-/W to /WE
gnd to /OE

I think that should be it? Am I missing anything?
here are a couple of pictures thus far. :) I still have to finish wiring it up.
This is in lue of YARRB. ;0). (Still hoping to get one).

No cringing at my design, I checked the 6502 after soldering it down and it's still working no problem. The Ram chip was definately working before I started to solder it in place, but it should be still fine... :). I was cautious about not applying too much heat to the pins and taking a few second break and then doing another pin on the other side of the chip.


image2.JPG
image1.JPG

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hoglet
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Re: My New Acorn Atom :)

Post by hoglet » Sun Jan 07, 2018 8:38 pm

waltermixxx wrote: R-/W to /WE
That's the one you need to be really careful about.

For reliable writes, the WE signal of a RAM should be R-/W gated with Phi2, like the NWDS signal on the on the Atom Schematic is (i.e. NWDS should be low, only when R-/W is low and Phi2 is high).

You could connect NWDS to the RAM /WE with a flying lead, or add an additional TTL device to your board to generate a local version. A 74LS00 should suffice, as would a 74LS139 (as per the Atom schematic).

Dave

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Re: My New Acorn Atom :)

Post by waltermixxx » Sun Jan 07, 2018 10:15 pm

I left room for a 16 pin chip :) just incase. :) (14 pin plus decoupling cap...) I will also add them on the daughter card for the cpu and ram chip :)

so I will add a 74LS00 :) Thank you :)
Last edited by waltermixxx on Sun Jan 07, 2018 10:40 pm, edited 1 time in total.

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roland
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Re: My New Acorn Atom :)

Post by roland » Sun Jan 07, 2018 10:19 pm

Why didn't you use sockets for the cpu and the memory?
256K + 6502 Inside
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Re: My New Acorn Atom :)

Post by waltermixxx » Sun Jan 07, 2018 11:39 pm

Because of the vero board I had on hand was only one sided. There was no way to solder the header to the daughter card board to ensure a good solid connection to the Atom. I basically did it with what I had on hand. The 6502 is a spare, i have a few (and it's still working fine) :) The 32kB static rams i have at least a tube of. I know it's not pretty, but I was eager to put something together. :) I wanted to keep the board small, didnt have enough space to mount both chips on the "bottom" of the board as the 6502 straddles the male 40 pin header that will plug into the Atom 6502 socket. I will add the 74LS00 and connect the inputs to the R/W and clock out pin 38 of the 6502 to the inputs. I will have to eyeball the schematic to sort out that last bit. :)

( Don't worry I wont make a mess of my Acorn Atom ) :)

Cheers. :)

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Re: My New Acorn Atom :)

Post by waltermixxx » Mon Jan 08, 2018 1:06 am

I noticed that there were two inverters on pin 39 of the PHI2 pin. Is that used to add a propagation delay or just buffer it (without inverting it)?

Would this be ok for my 32k ram upgrade, (this is from Briel's Apple 1 replica) :
32kram.png

could i use this as is, or should i add two inverters to the PHI2 before connecting it to the above?

Cheers. :)

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Re: My New Acorn Atom :)

Post by hoglet » Mon Jan 08, 2018 7:47 am

waltermixxx wrote: Would this be ok for my 32k ram upgrade, (this is from Briel's Apple 1 replica)
That should be perfect!

Dave

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Re: My New Acorn Atom :)

Post by waltermixxx » Mon Jan 08, 2018 7:20 pm

Thank you Dave,

Very much appreciated. :)

Cheers. :)

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Re: My New Acorn Atom :)

Post by waltermixxx » Mon Jan 08, 2018 9:10 pm

Ok perhaps a goofy question, and perhaps I should have asked before starting to build my very basic 32k ram daughter card. :) I've looked in the Technical Manual, and even Splitting the Atom documentation, and I guess I'm wondering:

Once I install the 32K memory and have memory from #0000 to #7FFF, will the 32K ram programs/games on the ATOMMC Program Compilation run? or are those games and programs setup to use paged memory somewhere in the #2800-3FFF space? like 4 pages of 8k or something along those lines. :) Or are they designed to work with basic 32k #0000-7FFF?

Just wondering if I'm wasting my time with such a simple design.... :)

Cheers. :)

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Re: My New Acorn Atom :)

Post by hoglet » Mon Jan 08, 2018 9:51 pm

waltermixxx wrote: Once I install the 32K memory and have memory from #0000 to #7FFF, will the 32K ram programs/games on the ATOMMC Program Compilation run?
They should work fine.

Dave

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Re: My New Acorn Atom :)

Post by waltermixxx » Mon Jan 08, 2018 10:03 pm

Once again. Thank you.

:0)

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Re: My New Acorn Atom :)

Post by waltermixxx » Tue Jan 09, 2018 3:50 am

Ok progress thus far. 8 address lines and a couple of CS lines to go. I know I'm drawing this out, (This thread, and this little project). But just like a good book, a good little wiring project makes me sad as I near the end. The book because I will miss the characters, and the little wiring project because I've most likely buggered a wire up and it won't work the first time. Lol.

I like to colour code the wires:

Red +5
Brown gnd
Address lines Blue
Data lines green
R-/w orange
CS will be yellow.


Here are my latest pics:
IMG_1211.JPG
IMG_1210.JPG

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Re: My New Acorn Atom :)

Post by waltermixxx » Fri Jan 12, 2018 3:20 am

Ok the 32k ram daughtercard is done. :) seems to work fine.
38933202664_d3e30850e9_k.jpg
39641677201_02e630862d_k.jpg
38745358965_a49c04c043_k.jpg
Wondering if Colour board should be next, or noise eliminator...

I'm thinking noise eliminator, as I dont think I ever used colour as a kid with the atom, plus I have this brilliant little black and white tv to go with it. :) it does the gray-scale for the colours really well. :)

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Re: My New Acorn Atom :)

Post by oss003 » Fri Jan 12, 2018 7:15 am

Nice job Walter ..... let the gaming begin ..... =D>

The easiest way to add a noisekiller is this one: http://www.acornatom.nl/atom_nieuws/198 ... 853086.htm
It also replaces the video buffers with more common 74LS244 and 74LS245 chips.

Greetings
Kees

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roland
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Re: My New Acorn Atom :)

Post by roland » Fri Jan 12, 2018 8:55 am

Good work Walter =D> It looks great.
256K + 6502 Inside
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Re: My New Acorn Atom :)

Post by waltermixxx » Fri Jan 12, 2018 6:00 pm

oss003 wrote:Nice job Walter ..... let the gaming begin ..... =D>

The easiest way to add a noisekiller is this one: http://www.acornatom.nl/atom_nieuws/198 ... 853086.htm
It also replaces the video buffers with more common 74LS244 and 74LS245 chips.

Greetings
Kees
I was thinking of going this route, once again on a small daughter card:

http://www.stardot.org.uk/forums/viewto ... =44&t=6003

i will use sockets on this daughter card, and use a protoboard with plated through holes. :)
and i would change the 74LS373 to a 74LS573 to make it easier. :)

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Re: My New Acorn Atom :)

Post by oss003 » Fri Jan 12, 2018 6:39 pm

Yes, that's the original design.
Please read primes note about the timing of the 123 and check that in the datasheets.

Greetings
Kees

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Re: My New Acorn Atom :)

Post by waltermixxx » Fri Jan 12, 2018 8:07 pm

Yup saw this:

One final note, is that different manufacturers LS/HC/HCT 123 chips have slightly different time constants, and the R and C values have to be calculated from the datasheet of the chip you are using.

Cheers.

Phill.

noisekiller.jpg
I know there is a ball park R (8.2k) / C (150pf) to value and to adjust according to the 74LS123 used. That will determine when to make the data lines available to the 6847 as per the timing diagrams on the Alan Knowles document. :)

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Re: My New Acorn Atom :)

Post by waltermixxx » Wed Jan 17, 2018 6:29 am

Regarding the 32k memory upgrade, I notice when I turn my Atom on, the screen says Acorn Atom initially, then after about 12 seconds, it changes to Acorn Atom + AtoMMC

Is that delay normal because of the extra ram?

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Re: My New Acorn Atom :)

Post by oss003 » Wed Jan 17, 2018 7:14 am

Not really, normally a reset signal causes the AtoMMC to generate an IRQ signal.
The Atom picks up the IRQ and jumps to #A000 to initialize the AtoMMC.
This does not always work fine because the BREAK key bounces and generates multiple reset pulses.
Every time the reset goes low, the AtoMMC is reset and that can cause problems.
Acorns solution for this was to add C11 to have a delay on pulling the reset line down but the value of C11 can be higher.
A scrambled screen at power on is also caused by not delaying the reset signal long enough.

Maybe the value of C11 is way to big in your Atom and causes a long delay.
You could try to another value of C11 (10 uF original and 20 uF for testing) and see if the problems are solved then.

Greetings
Kees

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Re: My New Acorn Atom :)

Post by daveejhitchins » Wed Jan 17, 2018 7:41 am

:shock: All the great add-ons for the Atom and there's still a problem with reset :shock:

Goodness Gracious! - Just nick the Beeb's circuit - I'm sure there's still room in the Atom's case, somewhere!!

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: My New Acorn Atom :)

Post by roland » Wed Jan 17, 2018 9:11 am

There's also a circuit with a TL7705 at http://www.acornatom.nl/atom_nieuws/198 ... 881075.htm
256K + 6502 Inside
MAN WOMAN :shock:

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