CPCWiki forum

Hello all,
I have just published a new version of the Amazing Demo with an additional part that introduces a comprehensive document on the CRTC (and a few other peripheral circuits).

This demo is compatible with all CPCs, regardless of their CRTC.
For the moment, the Amstrad Cpc Crtc Compendium document is in only available in French, but an English version is under preparation.

Please be patient (or misuse Google Translate  ;) )

https://demozoo.org/productions/302806/
http://logonsystem.fr/down/ACCC2-FR.pdf

WOW!


>170 pages of information. I am deeply impressed!


Unfortunately can't be translated as Google only accepts documents up to 10MB. Would you be able to publish it as HTML on a Website? With that, we could all translate to whatever language we prefer.

Looks amazing.  Eagerly anticipating the English version!  :)

https://youtu.be/QzRHXuVNXTs

For the people willing more details about what this release really means for the Amstrad community, I just updated my personal website with a dedicated news for this AMAZING effort from @Longshot (https://www.cpcwiki.eu/forum/index.php?action=profile;u=128) / LOGON SYSTEM :)

http://norecess.cpcscene.net/news/raaaaahhhh-the-amazing-longshots-comeback (http://norecess.cpcscene.net/news/raaaaahhhh-the-amazing-longshots-comeback)

Could you describe for a noob Z80 coder what happened here in short? I can see plenty of colors partly in Mode 2 (rasters?) In full screen. Even one line is separated in different colours. Impressive but I can't imagine the programming efforts behind.

Hello,

QuoteCould you describe for a noob Z80 coder what happened here in short?

In the upper part of the screen, the logo is in graphic mode 0.
In this part, the video offset on each line is updated with the possibility of accessing the majority of the central RAM.

More generally the old techniques were often limited to less than 50% of the RAM, whereas it is now possible to use 100%.
The CRTC 0 and 2 also have the unique capability to do this more easily than the CRTC 1, 3, and 4; they therefore have access to more CPU during the line.
The lower part is of little technical interest.
These are effectively just color changes for PEN 0 and 1 on each line.

A more interesting section can be found in the 6th part of the demo, which uses the most popular technique on CPC.
Here, the video offset is also updated on each line, but this process can only access 12% of the RAM; however, more CPU is accessible during the line.
This technique now works on the CRTC 2, which did not use to be the case.

QuoteWould you be able to publish it as HTML on a Website?

I will do my best to provide the English version as soon as i can (I do not wish to make the document available in HTML).

Thanks XeNoMoRPH for the YouTube video.  ;D

RAAAHHHHHHHHH! A (almost) new release by Longshot! The intro screen looks really good and I am so curious to read that documentation (once it has been translated into a normal language  :D ;) )

Quote from: BSC on 23:03, 02 December 21RAAAHHHHHHHHH! A (almost) new release by Longshot!

On a personal note, I think that's fantastic to see old legends of the early 90s - yes, both of you, @BSC (https://www.cpcwiki.eu/forum/index.php?action=profile;u=480) and @Longshot (https://www.cpcwiki.eu/forum/index.php?action=profile;u=128) - still around in the community -- 30+ years later. :) :) :)

Quote from: BSC on 23:03, 02 December 21
(once it has been translated into a normal language  :D ;) )

Greek?  :o

I've translated 50 pages so far(just using Google translate with some tidy up admittedly with my crap french, pic grabbing and reformatting) , plan to finish it soon, its a word doc, might be exportable as pdf.
Will not make available without Longshot's permission(not my work but I was curious of the content)

Fascinating read tbh.

I advise you to wait a little longer for version 1.2 to come out because I corrected some errors and added a lot of things (225 pages).
I will release the English version at the same time.

Quote from: Longshot on 23:53, 04 May 22I advise you to wait a little longer for version 1.2 to come out because I corrected some errors and added a lot of things (225 pages).
I will release the English version at the same time.

Ohh very nice, I was only translating for my own interest, as its been a while since OP, do you have any approximate release date of the English version?

If you're interested I can help with the English version of the 1.2 version, can send what I've done as example, was doing 17 pages per hour, language conversion, proof reading/ambiguity translation correction, redoing tables and charts.
I do write technical docs professionally to support my coding implementations, so I do have experience.

If I did help, I wouldn't be looking for any recognition or absolutely anything else, merely interested in spreading tech info.

Otherwise, no problem, very much look forward to the English version of 1.2.
Thanks

Thank you for this proposal. ;D
I will send you a PM.

Hello all,

I have just published version 1.2 of the compendium.
http://logonsystem.fr/down/ACCC1.2-FR.pdf

This version corrects some errors and addresses more specialized subjects, with in particular chapters on the gate array (highlighting the differences between the models), or even the precise management of i/o and interrupts by the Z80a, as well as new techniques (RFD=Rupture For Dummies, CRTC 1A/1B, Vertical Scroll at 1/64th sub-pixel, Interlace, R2.JIT/R3.JIT, ...).

The SHAKER test module in version 2.1 is related to this document.
http://logonsystem.fr/down/shaker21.dsk

The latest version of Amspirit emulator is currently able to correctly satisfy almost all the tests.
Thanks to DManu for the considerable work he provided on his emulator.

The English version is being corrected by Mark.
Give him time because there is work. Mark, thank you very much for your proposal ! ;)

For those who have a CRTC 1, they can possibly run SHAKE21B.BIN, and then press the "O" key, in order to know if their CRTC is a CRTC 1-A or 1-B. Currently out of 7 CRTC 1 tested, 3 were 1-B.

SHAKE21B.BIN also contains the demonstration of sub-pixel vertical scrolling ("0" (zero) key) at 50Hz (1/8, 1/16, 1/32, 1/64) which will only work on a monitor CTM and which would theoretically require a higher resolution than the best monitors can currently provide (in theory 272x64=17408 vertical pixels ;D )

Quote from: Longshot on 12:29, 26 May 22The English version is being corrected by Mark.
Give him time because there is work. Mark, thank you very much for your proposal ! ;)

I'm an emulator author who currently works as a developer, but before that career I was a writer and editor at a couple of different publishers, so drop me a line if you want any additional help. Otherwise I'll just keep my eyes peeled. Thanks in advance for putting so much effort into this!

The English version of the compendium 1.2 is available here:
http://logonsystem.fr/down/ACCC1.2-EN.pdf
Many thanks to Marc for his remarkable work.

Version 1.3 will contain at least revisions to CRTC 2, 3 and 4 interlace chapters.
English and French versions will be released at the same time. ;)

30 pages free

Quote from: Longshot on 09:50, 27 July 22The English version of the compendium 1.2 is available here:
http://logonsystem.fr/down/ACCC1.2-EN.pdf
Many thanks to Marc for his remarkable work.

Version 1.3 will contain at least revisions to CRTC 2, 3 and 4 interlace chapters.
English and French versions will be released at the same time. ;)

Thanks Serge

Quote from: TotO on 09:58, 27 July 2230 pages free

Lol, you made me panic, blank pages have been removed from the English version along with realignment of pages in the translation resulted in a reduced page count.

Quote from: TotO on 09:58, 27 July 2230 pages free

??

Version 1.1: 173 pages
Version 1.2: 226 pages (French/English)

226 -> 256

Just a "byte joke" about the free space left to add more content.

Kneejerk comment only: "Note that the American (and Japanese) format was the NTSC (National Television System Committee) with a horizontal frequency of 17,734 kHz and vertical of 60 Hz." is definitely not right; it's around 15.734 Hz since the introduction of colour, having been 15,750 Hz before that.

... and if that's the biggest error in the book — a typo of '7' for '5' and use of a comma as a decimal point — then I think you're on extremely solid ground. Thanks for putting so much work into this!

Thank you for this feedback.
I just corrected the error. I didn't know they changed the NTSC horizontal frequency to minimize interference between certain signals. (my source was wrong https://www.son-video.com/guide/les-standards-de-la-television).
I indicated the frequencies in Hz.
The point or the comma is definitely prohibited as a thousand separator. >:(

Do not hesitate to make other feedback if you notice other errors (there are some that I corrected in 1.3).

I re-uploaded the version with some corrections on cross-references that Winword had trashed.

The English version of the compendium 1.3 is available here:
http://logonsystem.fr/down/ACCC1.3-EN.pdf
Many thanks to Marc for his remarkable work.

In order to facilitate access to the results of the SHAKER tests, a portal was created:
https://shaker.logonsystem.fr/

Hello

A new version of the Compendium (v1.4, 269 pages) is available here:
http://logonsystem.fr/down/ACCC1.4-FR.pdf

The English version is under review.
Thanks to Marc for his remarkable work.
BSC, be patient ;D !!

The chapters relating to the "Interlace" mode, as well as several concepts relating to the VSYNC signal (e.g. a single-line lag in certain situations), have all been reviewed in depth.

The chapter on "tips & tricks" has been largely enriched (10 sub-chapters).

A new chapter dedicated to "fixed-time development techniques" has been added.

These techniques are one of the cornerstones of the work carried out to create the Compendium.

This new chapter is also a way to introduce the use of a CPU calculation function, described in the document.

SHAKER 2.3,  developed with the help of this calculator, is available on the logon system portal.
( 80 kb with 4 modules).

Results of the SHAKER 2.2 tests can be accessed here: https://shaker.logonsystem.fr/

I would like to take this opportunity to thank DManu for our positive, collaborative work.
Much more accurate than any other CPC emulator, AMSPIRIT perfectly simulates the "Gate Array/Z80/CRTC" trio of the old generations of CPCS for CRTCs 0, 1, 2, and 4, including all of the "Interlace" functions (unjustly ignored so far ;) ).

Cool. Looking forward to an English translation as the French is a bit beyond me. Really good technical documentation though. Hopefully we'll end up with definitive docs of how the different CRTC variants work and get better emulation and even more cool tricks as a result.

Great thing for people who want to get into CPC coding more seriously.  :) :) :)

Quote from: Longshot on 19:12, 12 January 23Hello

A new version of the Compendium (v1.4, 269 pages) is available here:
http://logonsystem.fr/down/ACCC1.4-FR.pdf

The English version is under review.
Thanks to Marc for his remarkable work.
BSC, be patient ;D !!

Are we there yet ? ...  ;D

Quote from: SerErris on 15:01, 14 January 23Are we there yet ?

Please be patient!

Learning French is easier than programming crtc, by the time you know crtc coding you will know all the French swear words too!

I already know one French swear!

Quote from: martin464 on 10:36, 19 January 23Learning French is easier than programming crtc, by the time you know crtc coding you will know all the French swear words too!

Learning French for 3 years as 3rd language in school, I disagree respectfully! :laugh:

Dragonbreed Wetware announced their second demo would include the first example of vertical rasters - but the demo never came out (as far as I know) - are you aware of that and is it possible?

Hello,

Is it what you called 'vertical raster' ?

example : https://www.cpc-power.com/index.php?page=detail&num=9101 (https://www.cpc-power.com/index.php?page=detail&num=9101)


Technicaly : The rasters are only horizontal. but we can get pixels on the screen that look like vertical rasters ;-)!

example : https://www.cpc-power.com/index.php?page=detail&num=7743 (https://www.cpc-power.com/index.php?page=detail&num=7743)

Quote from: zhulien on 16:57, 17 February 23Dragonbreed Wetware announced their second demo would include the first example of vertical rasters - but the demo never came out (as far as I know) - are you aware of that and is it possible?

I think they meant vertical rupture (http://www.cpctech.cpc-live.com/source/split.html).

Maybe you could ask PowerHowse (https://twitter.com/drpeterdenhaan) from Dragonbreed?

Hello

A new version of the Compendium (v1.5, 282 pages) is available here:
http://logonsystem.fr/down/ACCC1.5-EN.pdf
http://logonsystem.fr/down/ACCC1.5-FR.pdf

The document updates for version 1.4 and 1.5 in English have not yet been checked and corrected by Marc.
Thank you for your indulgence.

I will put online the version corrected by Marc once available.

The chapters relating to synchronization have been reviewed in depth, in particular on the nature of the CSYNC signal sent to the monitor by the GATE ARRAY.

The chapter on the states of CRTC's 3 & 4 has been updated with the identification of new states.

SHAKER 2.4 will soon be available on the Logon portal (....Be patient ).

SHAKER now demonstrates that it is possible to achieve smooth horizontal hardware scrolling in 1 pixel mode 0 and 1 pixel mode 1 without resorting to double buffering.

Results of the SHAKER 2.2 tests can be accessed here: https://shaker.logonsystem.fr/ 

 
The next version of the Amspirit emulator, developed by @DManu, reaches new heights of precision.
Amspirit should in particular consider the work on the composite signal and its management by the CTM. 
No emulator until now was able to handle an in-line CSYNC. ;)

Thanks for putting lots of work and effort in it!!!  :) :) :) :) :) :) :)

SHAKER 2.4 is now available on the Logon portal:
http://logonsystem.fr/html/downloadlogon.htm

The add-on disk (SHAKER_ADDON.DSK) contains two little programs:

- An example of a vertical rupture for all crtc's (already presented with 2.1).
- An example of an hardware horizontal scroll at the pixel level in graphics mode 1.

That scrolling is amazing, is there a catch?

For game developing, of course there is a catch, you need to sustain the fx in every scanline that you want that fx.

Aside of that, you need extreme timming accuracy, because you need to set R3 = 5 and then R3 = 6 during the HSync period (that simulate the display shift per one pixel).

Of course, you can not forget, that your screen is going to shake one pixel  in horizontal, then you need to blank those columns if you can not hide them outside the screen borders (take a look to the AMAZING Relentless in Winape with "show interrupts" enabled).

And last, if you are using a HUD after the scroll zone, then you need a few scanlines between the zones for letting the CRTC resynchronize again and the start of your HUD is not shifted by the display resynchronization.

It is not impossible, but your engine need to be built around these limitations.

@Longshot it looks like that logonsystem.fr is down?

I am getting this page:
(about:invalid)

Does anyone have a copy of the 1.5 compendium (english)
http://logonsystem.fr/down/ACCC1.5-FR.pdf (http://logonsystem.fr/down/ACCC1.5-FR.pdf)

Quote from: SerErris on 11:17, 25 July 23@Longshot it looks like that logonsystem.fr is down?

I am getting this page:

Sorry about that. I am changing providers.

You can download version 1.5 here.
http://logon.system.free.fr/down/ACCC1.5-EN.pdf

Nothing to apologize .. Thanks for providing the document and the link.

Actually thanks for doing the hard work on all of that. Really one of the best documents for the CPC in its entirety.

A new version of the Compendium (v1.6, 284 pages) is available here:
http://logon.system.fr/down/ACCC1.6-FR.pdf (http://logon.system.fr/down/ACCC1.6-FR.pdf)
http://logon.system.fr/down/ACCC1.6-EN.pdf (http://logon.system.fr/down/ACCC1.6-EN.pdf)

A new version of the Compendium (v1.6, 284 pages) is available here:
http://logon.system.free.fr/down/ACCC1.6-EN.pdf
http://logon.system.free.fr/down/ACCC1.6-FR.pdf

(cannot edit my previous message to correct the link :o )

I'm reading the English translated version of the docs, it's a lot of knowledge in one place.
I have some difficulty about understanding R.F.D. (chapter 11.5).
It says
"It is important to note however that if the condition C0=R1 is not met (because R1>R0), then the
condition C9=R9 is enough to deactivate the update of VMA with R12/R13. It is therefore not
enough for R1>R0 to be able to modify the offset on each line."
However the DSC4 demo sets only R5 once in a frame, but C9=R9 condition happens a lot (R9=07), and RFD still should not turn off (as it would break the demo).
So in this demo, what would be the deactivate condition? Isn't C9=R9 should be C9=R9 _and_ C4=R4?

I just wanted to say a really heart felt "THANK YOU!" to Longshot and everybody else who might be involved in that project!  8)

I really learned a lot reading through it, even when not everything made complete sense to me and may need some code testing to fully grasp how that all plays together.
But this is one of the best and most detailed documentation for a retro computer I ever read!

THANK YOU!

@Appolo: Thank you for your appreciation. It's encouraging to have positive feedback on my work. ;D

@slingshot: I think that the "sick mode" that you apply is nonsense.
This explains the regressions you encounter on Mist with other demos.
"Sick mode" is the simple observation of a phenomenon that remained unexplained until the Compendium.
In effect, an unexplained phenomenon had been detected when setting R5>0 on C0=R0.

The Compendium explains and documents all of the CRTC logic behind this bug since version 1.2.
This has given rise to a new technique called RFD that allows you to modify the offset on each line on the CRTC 1.
The answer to your question is found in the sentence following the one you quoted.
You just need to read the chapter completely to understand how it works.
This is how DManu78 implemented it correctly in Amspirit.

Version 1.7 of the document is available at https://shaker.logonsystem.eu

Thanks for your continuing great work!  :) :) :)

hello @Longshot i read you compendium but my english level is too low to understand it. do you plan to translate it in german  ?

also i asked some thing about your last demo called BSC 4, can you help me plaese man ?

hello @Longshot again, as you don't do the answer, i guess you are translating the pompendium in german  ?
i see BSC like my previous post, are you the man who found the title of the logon demo?

Why are you claiming, that you are german?
Your english has nothing to do with a 1:1 stupid translation between english and german (e.g. "i am in the disappoint", which may be a primitive translation from another language, but very probably not from german).

Quote from: Bug Powell on 11:57, 10 November 23do you plan to translate it in german  ?

Longshot created the document in French and someone else is doing the English translation with the help of Google Translate and some (a lot of?) manual polishing. If you're keen to get a German translation you could do the same with a German translation of the document and provide the result to the community.

I would use DeepL for that, which should be much better. 

Even the English version is hard to read as the translation from French created some strange sentences, that you would never say in english.

You can use even ChatGPT for a translation as it understands context much better after you explained it.

This is the outcome of DeepL, which normally does a pretty good job, but fails here, the genders are wrong (as neither CRTS, nor GATE ARRAY are known to DeepL)
Auf dem AMSTRAD CPC beträgt die Dauer eines CRTC-Zeichens 1 µsec.
Dieses CRTC-Zeichen repräsentiert 2 Bytes im Speicher.
Der Speicherzeiger wird von der CRTC an das GATE ARRAY übermittelt, das immer den 64k "Zentralen Ram" lesen wird. Der GATE ARRAY kann keine Daten aus dem ROM oder RAM lesen, dem zusätzlichen RAM des 6128 (oder der Speichererweiterungen).
Die CRTC ist so programmiert, dass das so erzeugte Bild von einem Monitor unterstützt wird. Eine sprachliche Abkürzung besteht darin, den Begriff NOP anstelle von µsec (Mikrosekunde) zu verwenden, da dies die Zeit ist, die diese Anweisung in Z80A benötigt.
Auf dem CPC werden Z80A-Anweisungen ausgerichtet, indem die M-Zyklen einer Anweisung auf ein Vielfaches von 4 T-Zyklen aufgerundet werden. Diese Ausrichtung hängt damit zusammen, dass der GATE ARRAY die Z80A unterbrechen muss, um auf den Ram zuzugreifen, dessen Adresse von der CRTC geliefert wird. Diese Funktionsweise verlangsamt einige Befehle im Vergleich zur Taktfrequenz. Um einen genauen Code zu erstellen, müssen Sie die genaue Zeit kennen, die jede Anweisung benötigt. In Kapitel 25 auf Seite 270 finden Sie detaillierte Angaben zu den Zeiten für die einzelnen Befehle.

This is the outcome of Chapter 4 from ChatGPT (German):
Bei AMSTRAD CPC dauert ein CRTC-Zeichen 1 µs.
Dieses CRTC-Zeichen entspricht 2 Bytes im Speicher.
Der Speicherzeiger wird vom CRTC an das GATE ARRAY übermittelt, das immer den "Hauptspeicher" von 64k liest. Das GATE ARRAY kann keine Daten aus dem ROM oder dem zusätzlichen Speicher der 6128 (oder Speichererweiterungen) lesen.
Der CRTC ist so programmiert, dass das dadurch erstellte Bild von einem Monitor unterstützt wird. Eine sprachliche Abkürzung besteht darin, den Begriff NOP anstelle von µs (Mikrosekunde) zu verwenden, da dies die Zeit ist, die dieser Befehl im Z80A benötigt.
Auf dem CPC sind die Z80A-Befehle so ausgerichtet, dass die M-Zyklen eines Befehls auf ein Vielfaches von 4 T-Zyklen gerundet werden. Diese Ausrichtung ist auf die Notwendigkeit des GATE ARRAY zurückzuführen, den Z80A zu unterbrechen, um auf den Speicher zuzugreifen, dessen Adresse vom CRTC bereitgestellt wird. Dieser Betrieb verlangsamt bestimmte Befehle im Vergleich zur Taktfrequenz. Um präzisen Code zu erstellen, ist es erforderlich, die genaue Zeit zu kennen, die jede Befehl benötigt. Siehe Kapitel 25, Seite 270, für Details zu diesen Zeiten für jede Befehlsanweisung.

Looks much better and I only need to tell ChatGPT that the GateArray is neutral in German.

Quote from: Longshot on 00:11, 26 July 23A new version of the Compendium (v1.6, 284 pages) is available here:
http://logon.system.free.fr/down/ACCC1.6-EN.pdf
http://logon.system.free.fr/down/ACCC1.6-FR.pdf

(cannot edit my previous message to correct the link :o )

@Longshot if you are willing to share the word document with me, I will translate it to german.

Send me a PM if you are interested.

I do have the Rosetta stone to help me to understand the original French meaning, without speaking French. So a little bit of Latin + the bridge via the English translation will make it simpler. However without the word version (or whatever text version you have used, all the page numberings will get wrong as german is not the same length in wording than french or english.

Wow,

chatGPT can actually translate whole pages .. so that should not take to long to do the job. 

Quote from: Prodatron on 21:45, 14 November 23Why are you claiming, that you are german?
Your english has nothing to do with a 1:1 stupid translation between english and german (e.g. "i am in the disappoint", which may be a primitive translation from another language, but very probably not from german).

Ich benutze eigentlich keinen Übersetzer, um auf Englisch zu schreiben. Ist mein Englisch so schlecht? Entschuldigung dafür!

Ich habe das Gefühl, dass @Longshot sehr verächtlich zu den Leuten ist. Ich habe höflich nach Infos über seine Demo und das Compendium gefragt, und er hat nie geantwortet. Denkt er, dass er mir überlegen ist?

@SerErris Ganz Deutschland wäre Ihnen sehr dankbar, wenn Sie es ins Deutsche übersetzen würden!

So @Longshot ... Guten Tag?

@SerErris: Thank you for your offer.

Marc (@Imimmfn) had worked to correct the English version.
He had spent time on version 1.2 and made some updates in version 1.3.
Since then, he has not been able to work on later versions.
Subsequently, my English version has probably regressed since version 1.3.

As @eto rightly states, I use Google Translate with a few small corrections.
What I have observed is that it is complicated to manage revisions between 2 translations when the gap between version numbers increases.
As such, I'm not sure it's a good idea to translate the Compendium into other languages, as this risks multiplying the problem of updating the document depending on everyone's availability; it would be better to improve the English version if it still has problems.

I think that Germans, in general, are more gifted than French people in English.
For example, in English, they naturally do not put a space before question marks, as a French person would.
Also, with the exception of the "clown" ;) , it shouldn't pose too much of a problem for a German to use the English version.

Version 1.7 of the Compendium is available here:
https://shaker.logonsystem.eu/ (https://shaker.logonsystem.eu/)

The problem is that the french version is something I cannot understand at all. So I can obviously read the english version, but also would do that service. And yes, you probably need to have a proper word document and enable versioning (track changes) in word to enable others to identify all the changes that potentially need updateing in the next version.

But to be honest, that should not be a  big issue. 

@Longshot what is the original document format and can you release it as well?

@SerErris
Marc is already revising version 1.7 in English with track changes enabled.
I do not want the original manuscript circulating or being modified by anyone else.
Thank you for your understanding.

Hi @Longshot,

thank you again for all the work in the Compendium. It is a fantastic source of all kind of information but esp. about CRTCs and the GateArray and stuff.

After reading a bit, I stumbled over the english Version page 26, where it reads in Chapter 4.4.4:

QuoteA cycle M consists of several T cycles, some of which place a wait signal in the active state to indicate to another circuit that the Z80A agrees that it should be slowed down. This wait cycle is commonly named Tw. This is particularly the case for the instructions:

• OPCODE FETCH, during the 2nd cycle T.
• Reading or writing memory, during the 2nd cycle T.
• IO REQ, during the 3rd cycle T.

Actually that is wrong.
The CPU does NOT signal with the WAIT line that it is ready to accept a WAIT state from external components, it is a pure input line..
In the Tw cycle it actually accepts a WAIT from another external component, or you could say only at this Tw cycle it honors an active High signal and runns Wait cycles until this line getting low again.
The next part is the actually correct:

QuoteWhen the Z80A "performs" a cycle Tw, it looks at its Wait line (in this case that connected to the gate array) and if it is active, then it will generate another cycle TW.

It might be a translation issue, but It looks like the same in french as far as I can decipher it. 

So again, I do not think anything is wrong in the document, but this sentence in particular can be missunderstood. Oviously that is no documentation for hardware designers, but another forumlation might be more clear on this.

Hello @SerErris

You are perfectly right. :picard:

It is of course the circuit connected to the Wait pin of the Z80A which sends a signal so that the Z80A takes it into account during its Tw cycles.

Thank you for this constructive feedback and I will of course correct the Compendium. ;)

QuoteA cycle M consists of several T cycles, some of which place a wait signal in the active state to indicate to another circuit that the Z80A agrees that it should be slowed down. This wait cycle is commonly named Tw. This is particularly the case for the instructions:

• OPCODE FETCH, during the 2nd cycle T.
• Reading or writing memory, during the 2nd cycle T.
• IO REQ, during the 3rd cycle T.

Checking this again, there seems to be also a mistake with T cycles.

A cycle M consists of several T cycles, that is correct. One of which is called Tw, where the CPU reacts to a signal on the WAIT input line. That we have discussed already.

But then the bullets are actually M cycles. It should read:
* Opcode Fetch, during the 2nd T-cycle of the first M cycle (M1)
* Reading, during 2nd T-cycle of second M cycle (M2)
* Writing, during 2nd T-cycle of 3rd M cycle (M3)

For IO operations, the CPU adds automatically a TW cycle, so that the read/write actually happens at the 4th T cycle which is T3 in nomenclature, but it is actually the fourth T-Cycle if you just count clocks.

It it is T1,T2,TW,T3 and @T3 the actuall read/write operation happens.
I am not 100% sure if that makes any difference, but would be correct.

Just saying. As I am creating a Memory Sniffer for debugging that is actually reading the CPC Bus and then starts reading everything into a memory block for later analysis of the running system, I needed to work with the timings of the CPU and when actually I can read the data from the bus, how long M1 is active etc. pp. 

This is for the Vortex Decrypting project, so that I can read the ROM from the actual running system. (e.g. see what the CPU sees, and recording it).

Please see timing diagrams attached from original Zylog product manual:
https://www.zilog.com/docs/z80/um0080.pdf

Has the compendium been taken offline?