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Author Topic: ZX Spectrum Emulator Card (Read 45025 times)

Offline gflorez

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Re: ZX Spectrum Emulator Card
« Reply #135 on: 2017.March.28. 01:02:27 »
This error was documented when I received the Spectrum emulator card, now at least more than a year back.

I made by myself a bridge with two edge connectors and a flat cable, following the official schematics.

Once all connected I powered on the computer. I had some games on a directory, so first I did a CD to it. Then I invoked  the emulator with :ZX.


Not knowing very much how it worked, I typed LOAD "" in Spectrum style...

At the prompt, I understood that instead a name, I could type an EXDOS command, so a :DIR or :BASIC could work.

With only a few lines the list of a DIR passed very fast. The selected game name loaded perfectly, but I'm not a gamer, so tried to load a second one. Then the first error happened, "File not found".

I tried another :DIR, but this time it returned garbage.

I typed :BASIC, and tried another :DIR from there. The same garbage.

I blamed my homely made bridge, and made some connection tests. Even I ordered a clone bridge from Pear. The same results.

Only that first time game load worked for me. You know I don't have a way to load from floppy, but I tested from Ramdisk and discovered the way to make the Emulator work.

Then I talked with Pear about another user problem like mine, but he didn't know more instances.

Then I bought another EP just to test  this and another problems, just to discard my old EP, but my tests returned the same results.



Basically, accessing the SD from the Spectrum emulator corrupts its lecture, not the content, that is preserved. The corrupted lecture, once produced, persist on Basic, EXDOS or ISDOS. Only a hard reset fix it.

I have tried a number of different SD cards and formats, always  the same.

It seems to me like a software error, but the first perfectly loaded game annoys me.

They aren't the games, only from where they are loaded.


Offline Zozosoft

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Re: ZX Spectrum Emulator Card
« Reply #136 on: 2017.March.28. 09:27:17 »
It is very strange! I afraid something hw problem with your Emulator.
My both Emulator (modified original, and new from Pear) works normaly with SD.

Offline gflorez

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Re: ZX Spectrum Emulator Card
« Reply #137 on: 2017.March.28. 09:58:54 »
Ok, I will talk with Pear.

Offline SzörG

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Re: ZX Spectrum Emulator Card
« Reply #138 on: 2017.April.02. 12:50:50 »
Hi All! I'm looking for solution :-)

Short result of the test of Pear's Zx Spectrum Emulator card on video, but i writting what you see here:

- test with and without external PSU, not affect the operation.
- The first and bigest problem, i test with a six Ep128 machines, the emulator working only with two machines.
The reason is, the additional ROM content does not seems.
- I pin up the System Bus Bridge - the machine speed is reduced to 3,04Mhz.
- I pin up the Emulator too - if the speed is not reduced even less, then the emulation can not started.
- If the speed reduce to 2,97 - 2,96 Mhz then the emulation can strated.
- The red LED of the Emulator card flashes to rhythm of keyboald pressing, and any graphics changes.

https://youtu.be/wMVZ1uSuaWE

Offline Zozosoft

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Re: ZX Spectrum Emulator Card
« Reply #139 on: 2017.April.02. 15:55:33 »
Very strange!

It is only my emulator card works normally? :oops:

Offline pear

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Re: ZX Spectrum Emulator Card
« Reply #140 on: 2017.April.03. 17:24:45 »
I have several pieces of these emulators yet.
How should the LED behave ?
How does the emulator affect the processor frequency ?
Maybe it only affects the measurement ?

Offline Zozosoft

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Re: ZX Spectrum Emulator Card
« Reply #141 on: 2017.April.06. 19:06:21 »
I'm very sorry! :oops: :oops: :oops:

The strange works of the LED are my fault! :oops: :oops: :oops:

In the schematic I draw it to wrong 74LS74 gate :-(
In the text and on the photos are the right gate used. U11 pin 8 are the right instead the U15 pin 8.

I corrected on my Pear type Emulator, and now it is 100% working like as the modified original.

For the other strange problems I not have too much idea :oops:
The CPU speed test of my memory test is counting in infinite loop between two video IRQ-s.
Code: ZiLOG Z80 Assembler
  1.                 LD HL,0
  2.                 LD IX,IRQ1
  3.                 LD BC,30B4H
  4.                 OUT (C),B
  5.                 EI
  6.                 HALT
  7. IRQ1            LD IX,IRQ2
  8.                 OUT (C),B
  9.                 EI
  10. IRQW            INC HL
  11.                 JP IRQW
  12. IRQ2            DI
At 0038h are JP (IX) instruction.

If this measure detect lower CPU speed, then probably false IRQ generated by the Emulator. Or generating WAIT signal which is slow down the execution.
Normaly the IRQ line and WAIT don't used. Probably PCB production problem, and there is some short circuit on SzörG's card?

At Gflorez's card: if the card also react to segment 07h writes as Spectrum attribute write, then it is can destroy the system areas of the SDEXT. This is can make SD card unreadable until the next cold reset.
« Last Edit: 2017.April.07. 11:40:21 by Zozosoft »

Offline pear

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Re: ZX Spectrum Emulator Card
« Reply #142 on: 2017.April.07. 11:26:49 »
Thanks for the checks and informations :)
WAIT signal is not connected in the ZX Spectrum Emulator.
« Last Edit: 2017.April.07. 11:34:45 by pear »

Offline gflorez

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Re: ZX Spectrum Emulator Card
« Reply #143 on: 2017.April.08. 02:27:23 »
I have also fixed the LED, thanks.



Now that I have a third EP (128KB) from a friend, I have made some test with the SD-reader+SpectrumCard combination.

At first the same problems with the SD access on two of them and surprisingly the emulator not starting on my new EP without apparent cause. 


But suddenly, on one of the hundreds of swaps(I only have a SD-reader and a Spectrum card), my old EP started to work without errors, making DIRs or loading games. After half an hour without problems, I have continued testing the other EPs.

Another swap and the next EP returned to fail miserably.... But sometimes disconnecting the devices and re-connecting them again, the miracle happened...

At the end I have made work the combination on the three EPs at least one time.


----------------------------------

Conclusion.... I think this is again a problem with the damned edge connectors.

Sorry for creating a false issue.


Offline pear

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Re: ZX Spectrum Emulator Card
« Reply #144 on: 2017.April.08. 07:10:38 »
Easy. By the way, I corrected the bug on the emulator schema.

Offline gflorez

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Re: ZX Spectrum Emulator Card
« Reply #145 on: 2017.April.09. 07:01:28 »
I have in my hands the Spectrum emulator card from Sinclair200. I will also fix it the led.

Offline Zozosoft

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Re: ZX Spectrum Emulator Card
« Reply #146 on: 2017.April.15. 21:01:58 »
At today Enterprise Club we tested SzörG's Emulator (from Pear):
Very interesting results! The Bridge from Pear do the machine slow down effect! :shock:
Not only the MHz display in EXOS 2.4 affected, the machine speed noticeably slower when this bridge connected.
On SzörG's machine the emulator don't detected (no ZX in the HELP list), both with the new and the original bridge. Original EXDOS card worked on this machine.

On another machine we got same results as Gflorez: can't load Spectrum programs form SD card, got a Cassette CRC error, and SD card still unreadable until cold restart. From RAMDISK it is working.
It is tested with both Bridge.

Very strange... :shock:

Now I got the SzörG's Emulator and the new Bridge, and will test on my machines, and comparing with my working Emulator.


Offline gflorez

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Re: ZX Spectrum Emulator Card
« Reply #147 on: 2017.April.15. 22:34:58 »
I have the  clone Bridge from Pear, it works very good for me. I don't have any noticeable slowdowns, it even works very well at 10Mhz with the emulator card.

But I don't have an original Bridge to compare. May be Sinclair200 can help me with that.

I still have my homely made Bridge done with a wide strip cable and two female edge connectors(and a lot of soldering). It worked for me the very first time, but I have to look for it.

All the old file errors have gone now, surely the edge connectors have been polished and cleaned with all the extractions and insertions I have made.

I have plans to buy a can of a good contact-cleaner spray just to solve this annoying problem.

Offline pear

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Re: ZX Spectrum Emulator Card
« Reply #148 on: 2017.April.16. 15:32:50 »
Very strange. The bridge does nothing. They have only a step-down power converter.

Offline Zozosoft

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Re: ZX Spectrum Emulator Card
« Reply #149 on: 2017.April.16. 20:49:04 »
Very strange. The bridge does nothing. They have only a step-down power converter.
Probably the switching power converter do some signal interference?

I will look it with scope.