My New Acorn Atom :)

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

Post by waltermixxx » Wed Jan 17, 2018 8:21 pm

before I installed the 32k daughter card, no scrambled screen on power up.
and i got the Acorn Atom + ATOMMC right away. WIth the 32k ram daughter card I built, still no scrambled screen,
just Acorn Atom at the top, with a cursor... and If I do a shift break before 12 seconds have past, I still only get Acorn Atom at the top.
and it does reset... it's only since i created my daughter card, that there is this crazy 12 second delay, and it's pretty consistant...
I know it's not shorting anything. nothing seems intermittant, i can leave a program running over night, and it wont crash.

just an odd thing.... i wonder if it''s temperature related? I will have to start feeling some chips. :)

I may post a video on Youtube and link here... :) i will update this thread if I do. :)

thanks for all the replies... :)

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hoglet
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Re: My New Acorn Atom :)

Post by hoglet » Wed Jan 17, 2018 8:42 pm

Please do post a video of this. It does sound quite strange.

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Wed Jan 17, 2018 8:50 pm

Will do. :)

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oss003
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Re: My New Acorn Atom :)

Post by oss003 » Wed Jan 17, 2018 9:16 pm

Please check the 6502 pins for shortcuts or connections with the capacitor.

Greetings
Kees

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Wed Jan 17, 2018 11:24 pm

Here is a link to the youtube video.
hopefully it shows the issue...

https://www.youtube.com/watch?v=zzgItXsn9x0

no laughing at my commentary ;o)

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roland
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Re: My New Acorn Atom :)

Post by roland » Thu Jan 18, 2018 8:37 am

Is the power of the MMC2 board ok? Or is it increasing to appr. 5V after power on?
256K + 6502 Inside
MAN WOMAN :shock:

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Thu Jan 18, 2018 11:35 am

I will have to check. It did this with two separate power supplies. Both at least 2.amp. Both are from name brand devices. The output with no load was about 5.25. I have a Rigol DSO scope, so I can watch the NMI line. The light on the device does flash upon power up.

I could try issuing a link command to initialize the MMC2 interface as soon as I power the unit. To see if it comes up right after.

:0)

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oss003
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Re: My New Acorn Atom :)

Post by oss003 » Thu Jan 18, 2018 11:54 am

When are the leds on the AtoMMC blinking, at power on or after 12 sec?

Greetings
Kees

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Thu Jan 18, 2018 5:44 pm

they do their initial blinking on power up.
Pretty sure that is the only time they blink unless there is disk access.
pretty sure it does not blink at the 12 second mark when the heading on the tv changes from Acorn Atom to Acorn Atom + ATOMMC2

I will do more testing. :)

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oss003
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Re: My New Acorn Atom :)

Post by oss003 » Thu Jan 18, 2018 7:01 pm

That's good, the leds blink when reset goes low so your reset signal comes through without delay.
The only other thing I can think of is a delay on the IRQ signal. I read that you have a scope, can you check if there's a delay on the IRQ line ..... not the NMI.

Greetings
Kees

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Fri Jan 19, 2018 10:26 pm

so, update:

i put the DSO on pin 19 (IRQ) and i get a pulse on power on, when the display still says ACORN ATOM.
then i set the scope to trigger on a pulse, and watched it to see what happens when the display switches to,
ACORN ATOM + ATOMMC2. Nothing coming from IRQ, no pulse when the screen changes... so I don't think it's related to the IRQ. I think it may be some kind of a ROM issue?

to recap, on power up the little leds flash on the ATOMMC2
and the pin 19 on the PL8 goes high as well. so an IRQ is being generated on power up.
then after the 12-18 second delay, the screen changes to ACORN ATOM + ATOMMC2 and no flashing
and no IRQ generated.

Does this help at all?
It's a very interesting issue...
started when i introduced my 32k ram, pin to pin on the 6502.
with the exception of PHI2 and R/-W being gated to produce a reliable wright signal for the static ram.
I checked for shorts there are none...

the puzzling part is the 12 - 18 delay before the screen changes From ACORN ATOM to ACORN ATOM + ATOMMC2.
once this has happened, and I leave the computer powered on, if I unplug the power and plug it in again, it either starts at ACORN ATOM + ATOMMC2 or changes to it in much less time, depending on how "warmed up" the computer is, or charged up a cap may be? I guess my next step will be to monitor the cs on the A000 rom.
which i will have to get from IC23 pin 13... :)

one thing i noticed is that when the ATOMMC2 is unplugged, the ACORN ATOM + ATOMMC2 never comes up.
i will try pulsing the irq line and see if the heading changes to the ATOMMC2 ... :)

i will follow up. :)

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Sun Jan 21, 2018 6:05 pm

Is this normal?

Pin 5&6 appear to be shorted? (not shorting check between 5 and 6...
Pin 6 does not go into the pcboard but curls under, no connection to the pcboard,
and no connection from pin 5 to the pcboard. oddly enough there is a connection
between pin 6 of the chip to pin 5 of the pcboard, so I'm guessing this is a mod to the board.
I dont think anyone can miss a missing pin on the socket. :)

I was hoping this might have been the cause of the issue...

On the schematic this connects Y1 to Y2 on the IC1A of the 74LS139. Could this account for perhaps the SD card not initializing right away?
IMG_1258.PNG
IMG_1259.JPG
IMG_1256.JPG
IMG_1260.JPG

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sirmorris
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Re: My New Acorn Atom :)

Post by sirmorris » Sun Jan 21, 2018 9:37 pm

This is as designed. An error in the PCB means that I need to re-route a pin. It is perfectly normal and nothing to worry about. The chip in question here is an address decoder and it has nothing to do with SD card initialisation, that is handled by the PIC processor. MMC and SD cards are tricky beasts. If you have a problem with a particular card my advice would be to put it to one side and try another.

I hope this reassures you :D

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sirmorris
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Re: My New Acorn Atom :)

Post by sirmorris » Sun Jan 21, 2018 9:50 pm

one thing i noticed is that when the ATOMMC2 is unplugged, the ACORN ATOM + ATOMMC2 never comes up.
i will try pulsing the irq line and see if the heading changes to the ATOMMC2 ... :)
The interface generates an IRQ at power-on. No interface, no IRQ. No AtoMMC. As you might expect.

When the OS ROM enables interrupts at machine start-up then immediately the AtoMMC initialisation code should run. The IRQ is level triggered and so the interrupt would be caught at the right time. The IRQ is cleared as soon as a command is sent to the interface, which should happen as soon as the IRQ handler is entered. This also prints the banner and fixes up some vectors before allowing the standard Atom initialisation to continue. I've never stopped to consider what might happen if the IRQ arrives very late - as it looks like it's doing here...

I wonder if the IRQ is generated at interface start-up or if I wait until I've detected a card? If that is the case then that would explain this behaviour. Pulsing the line manually (through a resistor to ground) is an interesting test.

Try a different card is my advice in this case.

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Mon Jan 22, 2018 12:00 am

It's time to try a new SD card.

I will follow up when I have a chance.

Thanks again everyone.

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oss003
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Re: My New Acorn Atom :)

Post by oss003 » Mon Jan 22, 2018 8:07 am

waltermixxx wrote:to recap, on power up the little leds flash on the ATOMMC2
and the pin 19 on the PL8 goes high as well. so an IRQ is being generated on power up.
Are you sure IRQ is going high on pin19 PL8, because IRQ is high and has to go low to generate an interrupt .....

@Charlie, isn't the card recognised when the the green led is flashing at power up or BREAK because the green led flashed directly after power up or BREAK so there's no delay in the RST? Can you test it without a SD card, the message should be displayed immediately right?

Greetings
Kees

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sirmorris
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Re: My New Acorn Atom :)

Post by sirmorris » Mon Jan 22, 2018 12:48 pm

The green LED indicates an SD card access. If there's no card in the interface it won't initialise, so no irq. IIRC.

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oss003
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Re: My New Acorn Atom :)

Post by oss003 » Mon Jan 22, 2018 1:34 pm

Hmmm .... IIRC it displays ACORN ATOM + ATOMMC2 even without SD-card which means an IRQ is generated ....
I could be wrong ...... or is that the #Exxx version?

Greetings
Kees

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Mon Jan 22, 2018 3:26 pm

Pretty sure Ive checked it without an SD card, and it will not post Acorn Atom + Atommc2.
I will have to try again, to be certain. (memory fading and all...) :) I'm using the A000 version of the rom. :)

I will test tonight, when I get home from work. And test with another SD card as well.

Cheers.

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oss003
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Re: My New Acorn Atom :)

Post by oss003 » Mon Jan 22, 2018 7:58 pm

Just checked it on my Atom with AtoMMC rom at #Exxx and even without SD card, it displays ACORN ATOM + ATOMMC2 after a BREAK or power up.

Greetings
Kees

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sirmorris
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Re: My New Acorn Atom :)

Post by sirmorris » Mon Jan 22, 2018 10:42 pm

Code: Select all

    // start the clocks
    CLOCKINIT();

    // ensure all ADC channels, comparators are off
    ADCON1 = 0b00001111;
    CMCON = 0x07;

    TRISA = 0b11011111;

    // enable pullups on port B
    INTCON2bits.RBPU=0;

    // Make Port B an input. 
    TRISB = 0xFF;

    // lights out
    REDLEDOFF();
    GREENLEDOFF();
    LEDPINSOUT();

    // read config byte from EEPROM
    EEADR = 0xff;
    EECON1bits.EEPGD = 0;
    EECON1bits.CFGS = 0;
    EECON1bits.RD = 1;
    configFlags = EEDATA;

    if (configFlags & 0x20)
    {
      ASSERTIRQ();
    }
I stand corrected. The bootloader generates the IRQ early in its startup. No card state taken into account.

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Mon Jan 22, 2018 11:15 pm

I just plugged my ATOM in without an SD card, and yup after about 18 seconds, i get the Banner,
so my previous post was incorrect. Without an SD card, I do get the Acorn Atom + AtomMMC banner, after
the usual 18 second delay on a very cold boot.

I will try an other sd card, and see if that changes... but I suspect it wont...
I'm not going to remove my 32k daughter card and re-install the 7K of ram,
and see if it still does the 18 second delay, as I cannot be bothered....
I'm happy I have solid state storage, and if I have to wait 18 seconds for it....(after 36 years of waiting for it)
I'm ok with that...(for now...) :)

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roland
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Re: My New Acorn Atom :)

Post by roland » Wed Jan 24, 2018 2:35 pm

waltermixxx wrote: I'm not going to remove my 32k daughter card and re-install the 7K of ram,
You'd only have to remove the board and install IC's 51 and 52 (zero page) plus a 6502. The Atom detects if there's any ram at #2900 and if not it sets the program memory to #8200 (in video ram). Of course you cannot load any programs but at least you can see if the delay is still there. So the test is quite easy if you are really curious (like we are :wink: )
256K + 6502 Inside
MAN WOMAN :shock:

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Wed Jan 24, 2018 8:57 pm

Good point. :)

I hope to get to that some time soon, I still have to record my Acorn Atom experiences for Randy from 1982 when I first brought one home...
a special day indeed.... :)

cheers.

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Sat Feb 03, 2018 9:23 pm

I finally added colour to my Acorn Atom. I already had Zippster’s colour computer composite video out board, so I thought may as well try it out. And sure enough it works great. It is NTSC colour which works great for me. The only thing I had to do was remove the two rca jacks on the board as they interfered with my 32k ram daughter card.

Pictures:
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danielj
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Re: My New Acorn Atom :)

Post by danielj » Sat Feb 03, 2018 9:24 pm

Great work :) Are you loving it?

d.

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Sat Feb 03, 2018 11:01 pm

Yes I am. :) My Acorn Atom is very happy, and so am I. The only thing missing now, really is a noise eliminator. But I will save that for down the road, don't wanna do it all at once. :) It's funny, I'm almost 100% sure the Acorn Atom I had as a kid, did have the colour card, although I don't think i would have ever used it with a colour tv. I just remember that it had a big daughter card in the video section, and that all the chip sockets were fully populated.

:)

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Sun Feb 04, 2018 3:35 pm

As stated previously as a kid I never hooked up my Acorn Atom to a colour TV, as a result I’m not sure what looks right. I find in text mode the characters appear as a light green on a much darker green. Is this normal? Also I wonder about some of the text graphics with very black spaces. (Not the same darkish green background as shown below. I ask because the colour board was meant as a composite video out for the Coco 1 and it Coco 2. :0)

P.s. the only way to get nice vibrant colour is to adjust the display as set. If I reduce the saturation, then they yellow looks white and the colours look like crap so to speak. Same with brightness and contrast.

So adjusting the monitor has been done. :0). I’ve also adjusted the trim pot on the colour board and it appears to adjust voltage peek to peek. :0)



Cheers.
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waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Sun Feb 04, 2018 4:13 pm

Pictures comparing the colour output of the colour board to the monochrome output of the atom on pin 9-10 of video connector.

I thought the colour output would be grey scale on a B&W tv, but it appears to be “dotted” like with the Apple II (artifact colour)

At any rate here are images from my little B&W tv.
8E5A2834-D62A-4438-8874-55E74FCD7894.jpeg
B001653D-840D-4FC3-9081-96CD1D9076A1.jpeg
The above are from pin 9-10. Below are from the colour board.

C8D1435B-005E-4B55-B0D7-07A82A06187F.jpeg
46AB55FD-1E71-4DD3-9701-8E7AD1CCC306.jpeg
Cheers.

waltermixxx
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Re: My New Acorn Atom :)

Post by waltermixxx » Sun Feb 04, 2018 4:28 pm

Here is a snapshot from the scope with colour output and pin 9-10 mono putput.
below that is the image from the TV (using the colour output).
NewFile1.png
AB9C3741-7C67-488C-A4B4-388C5DEED7A5.jpeg
Cheers.

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