Torch Z80 Problems

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Bat
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Torch Z80 Problems

Postby Bat » Mon May 14, 2018 7:29 pm

Hi,
Dragging this back from the past as I've got pretty much the same issue and there's no solution on this one!
The screen shot with a few squares on it, I can get a full screen of them.
I've got an 8721 fdd controller and a torch V1.21 ABL ROM, the Z80 board has a CCCP V1.02 ROM.
I've had arrive today a Raspberry GPIO cable, but it's no different from the IDE cable I tried before.
Anyone please? :)
Cheers,
Gavin :)

Moderators note: Gavin is referring to an existing topic "BBC + Torch Z80 Help" Mark

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danielj
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Re: BBC + Torch Z80 Help

Postby danielj » Mon May 14, 2018 9:27 pm

Do you have an oscilloscope/logic analyser?

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Re: BBC + Torch Z80 Help

Postby Bat » Mon May 14, 2018 9:50 pm

Sillyscope yes, but more of a novice with that than a beeb though! :)

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Re: BBC + Torch Z80 Help

Postby Bat » Mon May 14, 2018 9:53 pm

Hi,
I mostly just get the no Z80 message. Sometimes it scrolls all down he screen other it does 3 or 4 then stops..
Cheers :)

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Re: BBC + Torch Z80 Help

Postby Bat » Wed May 16, 2018 7:19 am

Hi,
I've also got a Raspberry pi 3 that's running Rune Audio at the moment. It can be repurposed if it could be of use for diagnosis?
Cheers,
Gavin :)

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danielj
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Re: BBC + Torch Z80 Help

Postby danielj » Wed May 16, 2018 8:33 am

So, firstly make sure the ports are clean. Second thing that'd I'd suspect is the 6522 VIA - remove that and try it in a beeb. If the VIA's dead (they're not super-reliable when old) then replacing that should get things talking. Assuming the VIA's OK you need to start checking whether the CPU is getting a clock, and running initial code from ROM. Assuming that's OK then I'd probably try and work out whether the PIA is working, and if that's working then I'd start looking at the RAM...

d.

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Re: BBC + Torch Z80 Help

Postby Bat » Wed May 16, 2018 9:08 am

Thanks :)
I'll take a look and work through that list...
Cheers :)

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danielj
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Re: BBC + Torch Z80 Help

Postby danielj » Wed May 16, 2018 9:10 am

(I'd actually look to see if the processor's running first, but the 6522 is something you can check using your beeb, and not using an oscilloscope!)

d.

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Re: BBC + Torch Z80 Help

Postby danielj » Wed May 16, 2018 9:11 am

For checking the Z80 side of things, although not identical, this will be helpful! http://chrisacorns.computinghistory.org ... procSM.pdf

d.

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Re: BBC + Torch Z80 Help

Postby Bat » Wed May 16, 2018 10:51 am

Hi,
Would IPA and a cotton bud be suitable for cleaning?
Cheers :)

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Re: BBC + Torch Z80 Help

Postby DutchAcorn » Wed May 16, 2018 11:47 am

I had not read this thread before but it seems that you had a working CPM system in the first post and trouble began after upgrading the roms to newer versions. Is it silly of me to suggest going back to the known working configuration and pick it up from there?

It is unclear to me if you saw drive activity after issuing cpm commands from the cpm prompt. Did you ever try a “dir” command? For cpm to actually work you would need a cpm system disk, which probably has a different format than a disk formatted from BBC Basic / Acorn DFS. Also please note that *commands such as *help are built in, the disk drive won’t be accessed if you type *help.
Paul

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Re: BBC + Torch Z80 Help

Postby danielj » Wed May 16, 2018 12:07 pm

Thank goodness for fresh eyes... (I only ever find myself reading the bottom couple of posts in a thread)

Indeed - exactly as Paul says => put the original ROMs back in and see what happens.

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Re: BBC + Torch Z80 Help

Postby Bat » Wed May 16, 2018 12:21 pm

Hi,
Guys the start of this thread is someone else, not me! :arrow: Moderators note: Thread has been split, see the first post. Mark
I purchased my Z80 with the ROMs and the guy assures me it all works fine.
I have obtained some system discs but haven't tried them as the drive does nothing.
From a ROM perspective the only thing I could think of was that it may be incompatible with my 8271?
I've listed the specifics in my first post in this thread, perhaps in hindsight I should have started a new thread but as I'd searched and found this one, complete with pictures it seemed a good idea....
Cheers :)

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Re: BBC + Torch Z80 Help

Postby danielj » Wed May 16, 2018 1:11 pm

Confusion rules. :) By the sounds of things you have the right ROM in your machine, the ABL one is for the 8271. Back to checking if the Torch works... You don't need system discs to run CCPN - if it's all good, you'll get the CPN prompt (basically CP/M in ROM).

:)

d.

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1024MAK
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Re: Torch Z80 Problems

Postby 1024MAK » Wed May 16, 2018 3:11 pm

Bat wrote:Hi,
Guys the start of this thread is someone else, not me!
I purchased my Z80 with the ROMs and the guy assures me it all works fine.
I have obtained some system discs but haven't tried them as the drive does nothing.
From a ROM perspective the only thing I could think of was that it may be incompatible with my 8271?
I've listed the specifics in my first post in this thread, perhaps in hindsight I should have started a new thread but as I'd searched and found this one, complete with pictures it seemed a good idea....
Cheers :)

When trying to fault find, yes, it is always a good idea to start a new thread. Piggy backing on another thread can and does cause problems!

I've split the thread now... :D

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Re: Torch Z80 Problems

Postby 1024MAK » Wed May 16, 2018 3:30 pm

Bat wrote:Hi,
Would IPA and a cotton bud be suitable for cleaning?
Cheers :)

Yes if it is general grime or grease.
If the problem is oxidation on connector pins, try using an "ink" eraser. You may need to cut it up...

Mark
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Re: Torch Z80 Problems

Postby 1024MAK » Wed May 16, 2018 3:59 pm

If after cleaning the connector pins, you still have problems, then the next step is to remove and refit any/all of the socketed chips on the Torch board.

Next up, using your oscilloscope, I suggest the following checks/tests on the CPU.

Does the reset pin (Z80 pin 26) go from low to high at power-up.

For reference here is a pin-out of the Z80 CPU.
Image

Then test the following CPU signals/pins:

Remember, we are just looking to see which lines are active, don't worry about the actual waveform. Set the 'scope to 1V per division.

Pin Function
16 /INT
17 /NMI
18 /HALT
19 /MREQ (should be pulsing rapidly)
21 /RD (should be pulsing rapidly)
22 /WR (may be pulsing)
24 /WAIT
25 /BUSRQ (should be high)
26 /RESET (should be high, except for a very short time after power is applied)
27 /M1 (should be pulsing)
28 /RFSH (should be pulsing)

You can also test the address lines A0 to A15 and the data lines D0 to D7. A lack of activity is suspicious.

Mark
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Re: Torch Z80 Problems

Postby Bat » Wed May 16, 2018 5:01 pm

Hi,
Thanks for sorting the post out and the useful picture :D
I'll plug the scope in after tea and have a go, the scope will have more of an idea than me, but then maybe it'll teach me to stop messing about with ancient computers! :roll: :lol:
Cheers :)

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Re: Torch Z80 Problems

Postby Bat » Wed May 16, 2018 6:54 pm

Hi,
Look at me, it almost looks like I know what I'm doing! :shock: :lol:

IMG_20180516_194121.jpg


Anyway....
Pin number..... Status
26. Goes high
16. Goes high
17. Goes high
18. Goes high
19. Wavey line :lol:
21. Wavey line
22. Goes high until *MCP then wavey line
24. Goes high
25. Goes high
26. Goes high
27. Goes high until *MCP then wavey line
28. Goes high until *mcp then wavey line
End of report....
Cheers,
Gavin :)

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Re: Torch Z80 Problems

Postby Bat » Wed May 16, 2018 7:08 pm

Hi,
A0 to A15 activity present
D0 to D7 activity present
Pin 6 seriously intense wavey line activity!
This is after *MCP as I fitted the torch ROM one socket from the right so I can boot to basic.
Cheers :)

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Re: Torch Z80 Problems

Postby 1024MAK » Wed May 16, 2018 8:16 pm

So, it looks like the Torch board is trying to do something, the Z80 CPU is trying to execute a program.

Mark
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Re: Torch Z80 Problems

Postby Bat » Wed May 16, 2018 8:43 pm

Hi,
I've just tried replacing the 6522 as suggested. I pulled one from a beeb IC3 socket on a machine that has a RAM fault.
This chip in the Z80 board made no difference.
Mark, from what you had posted my limited knowledge bought me to the conculsion that it seemed to be working but for some reason the Beeb can't see it? Thinking more, dangerous ground here, I swapped the 6522 thinking this is the main thing connecting the Z80 to the beeb.
Does IC71 and 72 play any part with the Tube or are they soley for the 1MhZ bus?
Is there an ic, or a circuit in general, that reports the Z80 functionality back to the Beeb for it to give the no Z80 message?
EDIT : Would that be pin 23 BUSAK?
Cheers,
Gavin :)
Last edited by Bat on Wed May 16, 2018 9:17 pm, edited 1 time in total.

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Re: Torch Z80 Problems

Postby 1024MAK » Wed May 16, 2018 9:04 pm

The link between the two is via the 6522 VIA, controlled via the Beeb's CPU, and the 8255 PIO controlled by the Z80 CPU. The two interface chips (6522 and 8255) have their 'external' I/O pins connected between them. So that the two different CPU's can pass data between themselves.

Anything that prevents the Torch board from running, or anything that prevents communication between the Z80 and the Beeb will cause the error that you have.

IC71 and IC72 are only used for the 1MHz bus. The address and data lines of the Tube port are connected straight to the 6502 CPU bus. Some of the control lines do go via glue logic.

I'm mobile at the moment, which chips (apart from the ROM/EPROM) are socketed on the Torch board?

Mark
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Re: Torch Z80 Problems

Postby Bat » Wed May 16, 2018 9:18 pm

Hi,
Would pin 23 BUSAK be responsible for telling the Beeb it's all ok?
Cheers,
Gavin :)

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Re: Torch Z80 Problems

Postby Bat » Wed May 16, 2018 9:22 pm

Hi,
Z80, 6522 and 8255 and the ROM are the only socketed chips on this board.
Cheers :)

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Re: Torch Z80 Problems

Postby 1024MAK » Wed May 16, 2018 9:24 pm

There is no single signal that goes from the Torch board to the Beeb. All communications from the Torch Z80 go via data through the 8255 and 6522 chips.

The Z80 /BUSRQ and /BUSAK system is not used.

Mark
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Re: Torch Z80 Problems

Postby 1024MAK » Wed May 16, 2018 9:29 pm

Bat wrote:Hi,
Z80, 6522 and 8255 and the ROM are the only socketed chips on this board.
Cheers :)

I think, if you don't use (maybe have to disable) the Torch ROM in the Beeb, you should be able to adapt a program designed to test the user port 6522 VIA to test the 6522 VIA on the Torch board. You would have to work out the address (unless JGH lists it on his web site).

You can then use a meter, or 'scope to check the 6522 outputs (PA0 to PA7 and PB0 to PB7).

Mark
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Re: Torch Z80 Problems

Postby Bat » Wed May 16, 2018 9:53 pm

Hi,
I've copied this from JGH's website, but it doesn't mean much to me :(

Code: Select all

I/O Map:
&00 - Port A Data I/O, page ROM in
&01 - Port B Data I/O, page ROM in
&02 - Port C Data I/O, page ROM in
&03 - READ(82c55): Control WRITE: Control, page ROM in

&04 - Port A Data I/O, page ROM out
&05 - Port B Data I/O, page ROM out
&06 - Port C Data I/O, page ROM out
 on reading b7=TxRDY for PortA, b1=RxRDY for PortB
&07 - READ(82c55): Control WRITE: Control, page ROM in

&10+n - Z80 SIO
&18+n - Baud rate selection


At the hardware level,

On the BBC host:
6522 VIA is use for the I/O
Port A is set for input, PortB is set for output
CA1 active signals that data is present in PortA
CB1 active signals that data can be written to PortB
CA1 and CB1 go active on negative edge

On the CoPro side:
Z80 PIO used for I/O
PortA is output, writing to 6522's PortA
PortB is input, reading from 6522's PortB
PortC reads 6522's CA1 and CB1 handshake lines


Cheers :)

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Re: Torch Z80 Problems

Postby Bat » Wed May 16, 2018 10:25 pm


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Re: Torch Z80 Problems

Postby 1024MAK » Thu May 17, 2018 8:04 am

Any addresses that are below 0F hex and / or which refer to a/the 8255 (82C55) are Z80 I/O port addresses.
You are looking for the base address of the 6522 VIA in the Tube address range.

Mark
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