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#11
avatar_Bryce
Amstrad CPC hardware / Re: Designing and building the...
Last post by Bryce - Yesterday at 13:47
Quote from: Benedikt on 19:27, 14 May 24
Quote from: Bryce on 12:18, 14 May 24some work in this direction has been done in the past. I know I've seen details of a modern KC Compact design using all western 74 Series IC's, complete with a PCB layout. This could save you a lot of the initial groundwork. Maybe someone here knows where it can be found. If not, I can check my archives too.
I am only aware of a modern redesign of the expansion unit that contains the floppy disk controller and the upper 64 KiB of RAM.
If there is a redesign of the system board, too, that could indeed be interesting.

You're right. I was mixing it up with the Aleste 520 project. :(

Bryce.
#12
Quote from: SerErris on Yesterday at 12:05That is what you can get for that price and it is on the low end of usable, however still massively better than a multimeter for digital cirquits. You can actually see what the lines are doing (up, down etc). And exact timing (e.g. fractions of a µs) is not important here.

Also the next better suited would be a proper oscilloscope like the Rigol 1054z (or any other entry level brand and model). But you know, it is even used for 200-300€ .. So I did not recommend it here, but that would be actually my normal recommendation to get into an Oscilloscope.

Nowadays you can get the new Rigol DHO800 series, with the DHO804 the cheapest option. That goes for ~400 Euros. This is a huge upstep with 12bit resolution vs 8bit of the old Rigol and 100Mhz vs. 50Mhz.
Hi. I do appreciate the suggestion of the ZT-702S/ZT-703S. I'm just clueless regarding what level of oscilloscope is sufficient for this kind of work.

So I was a little disheartened to be told that the ZT-702S isn't really up to the job of helping to diagnose the issue here, after buying it for that purpose.

I've requested a return on the ZT-702S. Hopefully that will work out and I can spend the money on a Dandanator instead.

I can also almost hear the shouts of "replace the damn RAM chips" and to be honest it does regularly cross my mind to do this, but I would love for a positive confirmation via McArti0'd tests before desoldering anything.

I hope the above doesn't sound too ungrateful! Thanks again for taking the time to reply here.
#13
Quote from: mmldrm on 14:29, 16 May 24
Quote from: Bryce on 14:18, 16 May 24Bryce.
Ouch. That would be a bit disappointing. It's the one suggested on page 2 of this thread.

The spec shows 10MHz. Am I misunderstanding it? (Quite possible.)

The quick explanation is that the quoted 10MHz is for a sinewave signal. To measure and display a squarewave the bandwidth of the scope needs to be around 5 times the frequency of the signal. I won't go into further details here, because I wrote a more detailed article about this a while ago, which you can read here:  https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/understanding-retro-electronics/msg144677/#msg144677

However, as @SerErris quite rightly mentioned above, a 50MHz Scope will cost at least €200, even for a simple budget device.

Bryce.   
#14
avatar_eto
Hardware / Re: Expansions Port
Last post by eto - Yesterday at 12:53
Geht es jetzt um RAM Chip Tests oder um Auslesen des Speichers?

RAM Test:

Es gibt das Amstrad Diagnostics ROM. Mit dem startet der CPC in einem speziellen Modus in dem das RAM getestet wird. Voraussetzung ist allerdings, dass der Rechner soweit noch in Ordnung ist, dass er korrekt das ROM lesen kann. RAM speichern geht damit nicht. 

Speicher auslesen:

Ein Speicherabbild im laufenden Betrieb ermöglicht das Multiface II. Das übernimmt auf Knopfdruck die Kontrolle und speichert Speicher-Abbilder auf Diskette ab. 

Auf einem 6128 auch noch mit einem Umschalter erledigen, sofern die Programme, um die es geht, nur 64KB benötigen. Hier kann man im laufenden Betrieb hart die RAM-Banks physisch tauschen und einen Reset ausführen. Der CPC startet dann aus der bisher ungenutzten Bank und man kann per Bankswitching den Inhalt der anderen Bank auslesen.

Evtl. sollte es analog auch mit Speichererweiterungen gehen, die die ersten 64KB extern spiegeln => https://github.com/revaldinho/cpc_ram_expansion/wiki/Universal-Amstrad-CPC-RAM-Card Da könnte es ggf machbar sein, dass du den Modus wählst, in dem das RAM gespiegelt wird, dann umschaltest und einen Reset durchführst. Der bisher gespiegelte Teil sollte dann als Erweiterungs-RAM auslesbar sein. 
#15
Quote from: mmldrm on Yesterday at 09:21Thanks. Ok I got the 74LS02 set up on the breadboard. (Ignore 74HC02 - TinkerCAD had no 74LS02.)

Where is nCPU ADDR on the Z80? Not sure where to connect that.

Let me know if

1. IC118 should be replaced (i.e. not wires)?
2. should Z80 pin20 and pin24 still be connected?
Have You DM74 or SN74?

/CPU (nCPU ADDR)  Pin14 GA 40010 or Pin2 LS153 or Pin15 AY3 or Pin11 PAL 40030/1

1) wires is better.
2) NO. Now the Force is with us.

When CPC stops on address lines A15-A0 you will have address #7F89
Z80 Pins 5,4,3,2,1,40,39... is 30

Next on Pins
0,1,1,1,  1,
1,1,1,  1,0,0,0, 1,0,0,1
RD Hi, WR Lo, IORQ Lo, nCPU Lo, Pin1 244 Lo.

You can tests D0-D7 Pin2-Pin14 RAM chips
#16
avatar_genesis8
News & Events / Re: 25 years ago...
Last post by genesis8 - Yesterday at 12:23
Thanks Eto, seems my memory is bad as always as if he stated it was the same permission for CPC roms, I dont see why I would have sent him an email specifically for CPCEMU.

Logically, I suppose I just pointed these informations to Marco Vieth for CPCEMU.
#17
Yes there is a commercial available GA alternative. But Benedicts approach is to use "old" 80s technology to achieve the same instead of a microcontroller.

Building the GA in TTL logic like the KC compact did will overcome this topic. 
#18
Quote from: mmldrm on 14:29, 16 May 24
Quote from: Bryce on 14:18, 16 May 24Bryce.
Ouch. That would be a bit disappointing. It's the one suggested on page 2 of this thread.

The spec shows 10MHz. Am I misunderstanding it? (Quite possible.)
That is what you can get for that price and it is on the low end of usable, however still massively better than a multimeter for digital cirquits. You can actually see what the lines are doing (up, down etc). And exact timing (e.g. fractions of a µs) is not important here.

Also the next better suited would be a proper oscilloscope like the Rigol 1054z (or any other entry level brand and model). But you know, it is even used for 200-300€ .. So I did not recommend it here, but that would be actually my normal recommendation to get into an Oscilloscope.

Nowadays you can get the new Rigol DHO800 series, with the DHO804 the cheapest option. That goes for ~400 Euros. This is a huge upstep with 12bit resolution vs 8bit of the old Rigol and 100Mhz vs. 50Mhz.
#19
Duke's website is Duke
#20
avatar_zhulien
Classifieds / Re: Latest on ebay
Last post by zhulien - Yesterday at 11:35
Quote from: HAL6128 on 09:42, 30 March 24That price is nice.... :)
https://www.ebay.de/itm/134989142856
and the date was April Fools Day
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