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avatar_Chinnery

Amstrad GX4000 / Plus cartridge PCB

Started by Chinnery, 10:02, 27 May 19

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TotO

#25
Hi Shining,

Please, can you show it working?
I have tested and it doesn't work for me.

Thank you.
"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

Bryce

I use one of these all the time. It has always worked fine with any machine I tried it on.

Bryce.

schombi

My skills in soldering a fairly poor and I have no background in electronics, but I successfully managed to build me a working Batman the Movie cartridge. Thanks for sharing this project!

What I´m still struggling with: I was always under the impression that the ACID chip was always required to use a cartridge on the GX4000 and those chips are hard to get these days. How come this project lets you decide whether to run with or without the ACID chip?

Bryce

Quote from: schombi on 06:53, 09 January 22
My skills in soldering a fairly poor and I have no background in electronics, but I successfully managed to build me a working Batman the Movie cartridge. Thanks for sharing this project!

What I´m still struggling with: I was always under the impression that the ACID chip was always required to use a cartridge on the GX4000 and those chips are hard to get these days. How come this project lets you decide whether to run with or without the ACID chip?

The 74HC112 is setting the appropriate signals at exactly the right time, so the CPC thinks there's a valid ACID chip on the board.

Bryce.

schombi

#29
Many thanks! Has this been only discovered "recently"? Seems like a pretty simple solution. I always thought a more complex workaround (e.g. a CPLD) was required.

pelrun

#30
There's a flaw in the ACID design that's being exploited - the CPC signals that the input from the 'ACID' is wrong long enough before forcing a reset that you can flip the input you're supplying (via the '112) to make it happy again.
https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/acid-chip-inside/msg22291/#msg22291


bobmoo79

#32
Quote from: Shining on 09:55, 05 January 22
Quote from: TotO on 16:58, 03 December 21I have tested this schematic by curiosity, and it looks to not work at all. ;D

May be I have done something wrong...
I don't understand what does special your RC combination compared to the original schematic.


Perhaps my schematic was not clear, cause I missed to describe the signal on the RC-combination:


On the original oscillogram for acid reset (https://www.cpcwiki.eu/index.php/File:ACID_Init_by_Grim.png) you will notice that after startup the sin signal has to be high. Using the original schematic from nilquader, the sin signal after reset is 50% low or high cause it does not follow the reset at all. Now instead of pulling the RC to VCC, I used the CCLR signal not only for CLK+ but also for PRE at the flip flop to force the flipflop to "1" after reset. Also I lowered the time constant for the RC-combination.


I know quite some plusses where this always works and noone reported a single problem until now.


So for clarity, the RC combination is not being pulled to VCC but instead is tied to CCLR? Sorry for being dumb.
I built one of these with the R1 connected to VCC AND CCLR. Didn't work obviously and I presume it's because the RC combo is not able to do its thing (as it's pulled high always.

Cheers.

bobmoo79

#33
So is this the correct interpretation of what 'Shining' posted?
I've connect the top of the R1 to CCLR and CLK (R1 is no longer connected to VCC). I've changed C2 to 100pF.

Initially I tried a 74HC112 flipflop but read somewhere that it should be a 74AC112 as the other is too slow, which seems to contradict the success others show in their posts. Regardless I am now using a  74AC112N and it's still not working.


I spent time last night double checking my PCB against this schematic and it's correct as far as I can tell. I then started modifying it to see if I could try different interpretations of the info presented in this thread but I just can't get it to work no matter what I do.You cannot view this attachment.


Of course I have no real proof that the EPROM is flashed correctly, but I do know that 'EGecu Pro' verifies the EPROM against the ROM and shows it is correct.  Is there any trick to flashing the EPROM? I downloaded a bunch of BIN format ROMS from CPCMania and burned them (I've tried several). I also tried CPR format files (which I converted to BIN using CPRTools) but all I get is a black screen on the TV.

bobmoo79


tjohnson

Do you have a working original cart?  Maybe you could take the EPROM from there.  There are a couple of cartridge designs knocking about that work fine with the 74ac112

bobmoo79

Thanks for your reply. I do have a working copy of Burning Rubber that I could use in my circuit which could help with fault finding, but I'd rather not dismantle the case to access the ROM. I was hoping somebody could confirm my understanding of what Shining had posted and maybe take a look at my schematic.

Bryce

I'm not sure what schematic software you are using, but it looks like the VCC pins aren't connected to the IC's. I assume they are on your prototype board?

Bryce.

bobmoo79

Hi Bryce, thanks for responding.

I'm using EasyEDA to do the schematics and I do have VCC and Gnd connected to each of the ICs on the prototype board. 

My question is really about how R1C1 are connected. At the moment I have the top end of R1 connected to CCLR (as is the CLK for U2). Does this look about right? 

Raizing77

hi i'm trying to make this cartridge work without the chip acid
but without modifications it does not start on my cpc 464 plus what should I modify on the card that I did print?
do i have to do some sanding?
I am sure that the eprom written by me work because if I put the chip acid they start without problems
can someone just tell me the modicum to do?


eto

#40
Quote from: bobmoo79 on 12:25, 30 June 22So is this the correct interpretation of what 'Shining' posted?
I've connect the top of the R1 to CCLR and CLK (R1 is no longer connected to VCC). I've changed C2 to 100pF.

Did you ever get that to work? I want to implement the same design but I'm not sure if it's correct or not.

Quote from: bobmoo79 on 12:25, 30 June 22Initially I tried a 74HC112 flipflop but read somewhere that it should be a 74AC112 as the other is too slow

Can someone confirm that the 74AC112 is required? Or should the 74HC112 always do? Or: in which cases is the 74HC112 not sufficient? I have a cartridge here with a HC112 and it seems to work.


pelrun

The hack is exploiting a race condition, so while HC-series logic *might* work, it might also be marginal, fail altogether, or depend on the input voltage, ambient temperature or phases of the moon. So you'd want to be at least prepared to switch to a faster series like AC if you experience problems.

00WReX

I have only used the 74HC112, and had no issues at all.
The CPC in Australia...
Awa - CPCWiki

Kris

Hello,

I use 74HC112 and it perfectly work for me as well.
You cannot view this attachment.

bobmoo79

#44
Quote from: eto on 10:02, 05 January 23
Quote from: bobmoo79 on 12:25, 30 June 22So is this the correct interpretation of what 'Shining' posted?
I've connect the top of the R1 to CCLR and CLK (R1 is no longer connected to VCC). I've changed C2 to 100pF.

Did you ever get that to work? I want to implement the same design but I'm not sure if it's correct or not.

Quote from: bobmoo79 on 12:25, 30 June 22Initially I tried a 74HC112 flipflop but read somewhere that it should be a 74AC112 as the other is too slow

Can someone confirm that the 74AC112 is required? Or should the 74HC112 always do? Or: in which cases is the 74HC112 not sufficient? I have a cartridge here with a HC112 and it seems to work.


Hi ETO, no I didn't get my carts working in the end because life got in the way and I didn't get clarification in this thread about what the schematic actually is. From the other replies it seems the choice of IC is not a concern. I still intend to go back and revisit this at some point though, so would be interested to know if you get yours working (and how).

@Kris as yours work fine are you able to clarify the design, addressing my previous queries?
Could you post your design/schematic file here so that we can open it in our own software to check against our own?

eto

Quote from: bobmoo79 on 13:08, 05 January 23so would be interested to know if you get yours working (and how).
I didn't have a 100p capacitor yet - they should arrive in a few days. But I got curious now and tried it with a 470p capacitor that I had here. Seems it works. I tried it on two different 6128 Plus machines and had no problems. Also Reset works.

I compared our schematics and can't find a difference... so no idea why it's not working for you.

I'm using a 74AC112 at the moment

eto

#46
I just incidentally found the 74F112 (TTL) which are new old stock and MUCH cheaper than the AC112. They are also much faster than the HC ICs.

Are there any reasons why they could be a bad idea?

eto

In my current design I will add some flexibility, so a single PCB can be used for 1Mbit up to 8Mbit Eproms and also offer the option to add DIP switches to select different ROM images, if an Eprom holds more than a single ROM image. 

You can basically use it for anything from 64KB to 512KB ROM images and 1Mbit to 8Mbit Eproms.

My personal use case is to have a single System cartridge for my Plus that holds everything I could ever need, but of course you can also use it as a multi-game cartridge.

Btw: For this use case I just read yesterday on Facebook that a Multicartridge is available again. It's almost twice as big as a normal cartridge but can also hold two 8Mbit Eproms, which gives you access to e.g. 16 (original) games: https://github.com/zeus074/Amstrad_Multicart?fbclid=IwAR1Y5acw2JXlD7Lj_-oVmmmFXKxp1TZOorqEduaN-04Ssz4G5vX5jw_AjnA

Duca750

#48
Quote from: eto on 12:41, 06 January 23En mi diseño actual, agregaré cierta flexibilidad, por lo que se puede usar una sola PCB para Eproms de 1 Mbit a 8 Mbit y también ofreceré la opción de agregar interruptores DIP para seleccionar diferentes imágenes ROM, si un Eprom contiene más de una sola imagen ROM.
Básicamente, puede usarlo para cualquier cosa, desde imágenes ROM de 64 KB a 512 KB y Eproms de 1 Mbit a 8 Mbit.
Mi caso de uso personal es tener un solo cartucho System para mi Plus que contenga todo lo que pueda necesitar, pero por supuesto, también puede usarlo como un cartucho multijuego.

Por cierto: para este caso de uso, acabo de leer ayer en Facebook que un multicartucho está disponible nuevamente. Es casi el doble de grande que un cartucho normal, pero también puede contener dos Eprom de 8 Mbit, lo que le da acceso, por ejemplo, a 16 juegos (originales): https://github.com/zeus074/Amstrad_Multicart?fbclid=IwAR1Y5acw2JXlD7Lj_-oVmmmFXKxp1TZOorqEduaN-04Ssz4G5vX5jw_AjnA
 
Hello, does this design allow 74HC112 or is an original chip necessary? Can you share PCB file? Thanks!


Hello, does this design allow 74HC112 or is an original chip necessary? Can you share PCB file? Thanks!
First design works perfect for me with MC74HC112N


eto

Quote from: Duca750 on 18:54, 08 January 23Hello, does this design allow 74HC112 or is an original chip necessary?
74??112 - I have to confirm yet, if HC will work or if AC or F is required. I have ordered a set of ICs, so I can test that soon. 

I have not yet tested the final design and I need to check if it fits into any of the available 3D printed cases or if I have to adjust the design. A couple of weeks probably before I can release the PCB. 

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