ZX81 Clone Tynemouth Minstrel 3

Any discussions related to the creation of new hardware or software for the ZX80 or ZX81
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1024MAK
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Re: ZX81 Clone Tynemouth Minstrel 3

Post by 1024MAK » Wed Jan 08, 2020 8:57 pm

I don’t see any obvious reason why the Chroma should not work with the Minstrel 3. The only snag maybe if the Chroma is unable to output HC CMOS logic high levels, but that goes for any interface that you want to use (as everything was originally designed for use with TTL logic levels).
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Re: ZX81 Clone Tynemouth Minstrel 3

Post by mrtinb » Wed Jan 08, 2020 9:07 pm

You cannot have RAM enabled in the same area on the Minstrel and the Chroma. Chroma has DIP switches for this. Maybe the Minstrel has some jumpers for this setting on its device. However Chroma might need to have RAM enabled where screen and color is stored, for video output to work through the Chroma.
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

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1024MAK
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Re: ZX81 Clone Tynemouth Minstrel 3

Post by 1024MAK » Wed Jan 08, 2020 9:11 pm

mrtinb wrote:
Wed Jan 08, 2020 9:07 pm
You cannot have RAM enabled in the same area on the Minstrel and the Chroma. Chroma has DIP switches for this. Maybe the Minstrel has some jumpers for this setting on its device. However Chroma might need to have RAM enabled where screen and color is stored, for video output to work through the Chroma.
That should not be a problem, if the Chroma drives the ROMCS and RAMCS lines (both on the expansion edge-connector) high when it enables it’s own RAM (which I believe it does), the Minstrel 3 will then disable it’s on board memory in the same way that a ZX81 or TS1000 does. So no conflict :D

Mark

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Re: ZX81 Clone Tynemouth Minstrel 3

Post by vanpeebles » Thu Jan 09, 2020 12:37 pm

I was looking at these to go in one of those new zx80 cases. Are they any other alternatives/options?
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Re: ZX81 Clone Tynemouth Minstrel 3

Post by Paul » Thu Jan 09, 2020 12:41 pm

The minstrel 3 is ZX81 Size so it's not suitable for a ZX80 case.
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Re: ZX81 Clone Tynemouth Minstrel 3

Post by vanpeebles » Thu Jan 09, 2020 12:53 pm

Paul wrote:
Thu Jan 09, 2020 12:41 pm
The minstrel 3 is ZX81 Size so it's not suitable for a ZX80 case.
Well that helps with my plans greatly. Minstrel 2? I just guessed it was all interchangeable :)
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Re: ZX81 Clone Tynemouth Minstrel 3

Post by tynemouthsoftware » Thu Jan 09, 2020 1:05 pm

The Minstrel 2 and Minstrel 3 are both ZX81 shaped, so will not fit in a ZX80 case. They are designed to be used in a ZX81 case or standalone.

There are some ZX80 clones that are the right shape and size for a ZX80 case, but the Minstrel boards are not.

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Re: ZX81 Clone Tynemouth Minstrel 3

Post by vanpeebles » Thu Jan 09, 2020 1:13 pm

Ah, thanks for the info :)
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Re: ZX81 Clone Tynemouth Minstrel 3 56k

Post by Mustermann » Sun Jan 12, 2020 7:51 pm

Mustermann wrote:
Sat Jan 04, 2020 11:16 pm
The way to 56k:

As already mentioned I replaced the 32k x 8 SRAM(IC2) by an 128k x 8 SRAM.
As this doesn't fit into a 28 pin socket, I took a 32 pin socket and cut of the legs 1,2,31 and 32.
Pin 1 is Not Connected at the 128k chip, pin 2 is A16. As I decided to use up to 64k I connected both of them to VCC(pin 30 of 128k = pin 28 of board).

CE2 is high active and if connected to VCC it would enable the chip if /CE is low, So connecting pin 30 of the 128k to pin 28 of board that is connected to VCC does not cause any trouble.

Temporarily I connected A15(pin 31 of 128k) to VCC using a long wire.
I also connected pin 32 to VCC using a long wire.

For further use i cut of leg 22 of the socket(pin 20 of board) and connected the board as well as the socket to separate wires.
For now these wires were connected to each other some cm away from the socket.
/CS of the socket is connected to /CS of the board, but can be disconnected when needed.

This was tested, working and provide the Minstrel 3 with 32k of RAM as expected.
Next we need to tell minstrel that there are 7 blocks of RAM.
This can be done by changing data selector IC22:
56kdataselector.jpg
Next we need to prepare A15 in a way that will access lower bank(A15=0) in /M1 cycle and the bank selected by A15 in /RD or /WR cycle.

A simple option is this:
A15simple.jpg
A15simple.jpg (4.01 KiB) Viewed 1421 times
When DFILE is in 16k-32k range it can be accessed in /M1 cycle thru 48k-64k

If BASIC program grows DFILE may move into 32k-48k area. This won't work with that solution.

What we need is:

If A15(CPU) is low, A15(RAM) need to be low.
If A15(CPU) is high and /M1 is high A15(RAM) need to be high
If A15(CPU) is high, /M1 is low and A14(CPU) is high A15(RAM) need to be low(Access to DFILE in 16k-32k range)
If A15(CPU) is high, /M1 is low and A14(CPU) is low A15(RAM) need to be high(Access to DFILE in 32k-48k range)

That can be made by this addition:
A15FET.jpg
A15FET.jpg (6.07 KiB) Viewed 1421 times
I prefer to solve that using logic chips.
One solution to do that with one chip is using of an additional 74HC251.
I soldered it on the back of IC22 according to that schematic:
56k.jpg
I added R_N1 to be able to go to 64k and R_N2 to add a write protect for 8k-10k later on.
If you are not planning this both of them may be set to 0 Ohm.

So my minstrel is able to access 56k now.

Max
Attachments
Sysinfo56k.jpg
ZX81 issue 1 near to original state
ZX81 issue 1 56k internal ram UDG and WRX enabled
Minstrel 3 ZX81 clone 64k with battery backup, UDG, CHR$128 and WRX enabled

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Re: ZX81 Clone Tynemouth Minstrel 3

Post by tynemouthsoftware » Mon Jan 20, 2020 12:22 pm

Looks interesting. A couple of questions. What extra software can you now run with the 56K RAM that couldn't run before, and are there any programs which did run with 16/32K but will not work with the extra RAM? I have not found much software which needs more that the standard 16K, so trying to judge if it is worth adding this to a future Minstrel.

Also, what is the test program you are using, my googling ability has failed me?

Thanks,

Dave

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