(C) E.Milun (PAUL ATRIDES).
Connecting the modem "ALEGRO" (C-DOS).
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And now, dear readers, we will tell you how to connect the modem "ALEGRO" to your computer. Since its other name - "C-DOS" - has already taken root among the people, I will adhere to it from now on.
First, I would like to confirm the statements of the well-known tinkerer Mr. Kirill Gromov - the CDOS modem does not work with Scorpion. (Oh, do not be alarmed, _now_ it works. How to achieve this is described below.) But...
But the culprit is not Scorpion, as this gentleman claims, but... CDOS itself. And it does not work not only on Scorpions but on any computer where a normal port #FF is implemented.
Why does this happen? Let's figure it out. Any external device, which claims to be "external," must inform the computer during its operation: "I have started working, so all internal ports please do not worry." In short - the external device must inform the computer that it has "caught" the request to itself. Understand? Well, C-DOS _does not_ do this.
Now let's look at everything in more detail. So, the computer tried to access port #FFEF (the C-DOS port) and immediately received a response from two devices: from C-DOS itself and from the internal port #FF. This happens as follows. When reading the modem port on the address bus, address #FFEF (llllllll lllOllll) appears, since the decoding of the modem port is performed by just one signal A4, which is currently at 0, C-DOS, naturally, is filled with pride and begins to diligently output data to the data bus. All right, isn't it? At this point, the Scorpion port #FF rudely barges into this idyll. This "nasty" port starts to output its own data to the same data bus at the same time. That's it! Overlapping with the data from the modem, the attributes distort them. The unsuspecting processor takes its byte and tries to interpret it as information received from the marvel of modern technology - the modem. And, of course, it gets nothing!
Mr. Gromov's like-minded colleagues are joyfully rubbing their hands at this moment and maliciously saying: "Aha, we told you, warned you. Such an implementation of #FF is incorrect, buggy. Do it like we do."
At this point, it is time for us to intervene and say, "Wait a minute, let's figure it out." The decoding of the attribute port occurs according to all the rules of "good tone" - the IORQ signal (access to ports), DOS (access to TR-DOS ports), as well as the state of the 4 address signals A0, A1, A2, A3 are taken into account. So what is wrong here? Signals A0-A3 and A4 are at 1, IORQ is at 0, since it is a port request, DOS is at 1, since this is not a TR-DOS port. Moreover, the IORQGE signal (internal port sampling permission) is also at 0! And what, in your opinion, should #FF "think" if this is a completely normal request to it?
Of course, you can introduce signal A4 into the decoding of the attribute port, but what is the guarantee that when connecting some other device, you won’t need to introduce A3, A6, A7 there as well, in short, you won't need to do a COMPLETE decoding? There is another option - not to introduce the IORQ signal into port #FF (as Mr. Gromov suggests), but then another problem arises, which we wrote about in our first issue - it is no longer an attribute port, since the synchronization of the "processor - attribute port" pair is violated, i.e. sometimes instead of attributes, garbage will be read.
Isn't it easier to use such a sampling of the attribute port "to the fullest"? And all you need to do is make the external device, in this case - the modem, generate the IORQGE signal? And since the IORQ and IORQGE signals are interconnected, the appearance of 1 on IORQGE will lead to the fact that 1 will also be set on IORQ, and the sampling of the attribute port will not occur. In my opinion, this is a more normal way.
I remind you that similar "glitches with the modem" will occur not only in Scorpion but also in any other computer where port #FF is fully implemented, not according to Gromov's scheme.
But enough of theories. To the point. We need to make C-DOS generate the IORQGE signal, which informs the computer, or rather, all its internal ports, when they can work and when they should "shut up" (IORQGE=0 - internal ports work, IORQGE=1 - ports on the external device). On the Scorpion, such a signal is already brought to the system connector. If your computer does not have such a signal, do not despair; you will need a small piece of wire and... one resistor for its implementation, but more on that below (and the IORQGE signal will be useful not only for the modem).
So, here is the modification scheme for the C-DOS modem (which, of course, needs to be inserted inside the modem) to generate IORQGE. The scheme connects in parallel with the "standard" connection of the modem.
Transistors - KT361, KT315 or similar, the letter does not matter. The chip DD1 - type LE1, any series 155, 555, 631, 7533 or any other chip containing logical elements 2OR-NOT, you just need to consider the pin layout.
Signals A4, IORQ are taken from the system connector, and IORQGE is brought there as well. Moreover, A4 and IORQ are already connected to the modem (in Scorpion - contacts 24V and 17A of the system connector, respectively), i.e. you will actually need to add only IORQGE (in Scorpion - contact 13B).
If you are still not satisfied with the modem sampling by just the A4 signal and/or if the scheme provided above does not yield positive results, you can use a more complete decoding:
As you can see, you only need to add one chip DD2, containing at least three 2AND-NOT elements, for example, LA9 series SSS, 155, 155. DD1 is the same as in the previous scheme (for generating IORQGE). In total, for normal connection and decoding of the modem, you will need only two chips - LE1 and LA9. Signals A0, A1, A2, A3, DOS are taken from the system connector (for Scorpion - contacts 9B, 10B, 11B, 23B, 4B), and are the same ones used for decoding the attribute port in Scorpion. In this case, the modem will respond to any port whose address in binary form represents the number xxxxxxxxxxl0xlll, and is not a TR-DOS port. If your DOS signal is not brought to the system connector and you do not know where to get it, you can instead introduce, for example, A6, A7, ..., or even just apply +5V. In principle, this should not affect anything, as there are no TR-DOS ports with similar addresses. The A4 signal is the same as originally brought to the modem, i.e. it is taken from the system connector or from the connector on the modem. The latter option is preferable.
The resulting MOD signal is brought to the modem (and to the IORQGE generation scheme, which is now part of the modem) instead of A4, that is, the A4 track on the modem is cut from the part connected to the computer, A4 is taken, and MOD is connected to the other. This is shown in the following diagram:
A4, from the cut A4, to the computer modem
■■■■■■■■■┬■■■■■■■х■■■■■┬■■■■■■■■■■
│ │
│ │
A4, to the MOD scheme, from the decoding scheme
Now about how to make the IORQGE signal in other computers.
The scheme is simple to the point of idiocy:
signal IORQGE 560 Ohm signal IORQ
(system connector) (pin 20 of Z80)
The IORQGE signal is brought to the system connector (for example, in Scorpion, this is 13B in the 60-pin connector), and the IORQ signal is connected directly to the microprocessor (to the track, of course). That's it, now you can connect anything to your computer. And if it informs the computer about its operation at the right moments, everything will be "hockey".
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MUSIC BY: GYN
Contents of the publication: Oberon #04
- From the Editorial
This editorial discusses the legal 'charges' against the creators of Oberon #4 as a humorous narrative, highlights the challenges faced in publishing this issue, and announces a potential hiatus for the magazine.
- Scroll
Analysis of the game 'Chaos' by Julian Gollop. Simplified gameplay mechanics and strategic elements. Description of creatures, spells, and tactics.
- Scroll - Unbeliever
Description of a mathematical game for ZX Spectrum where players collect formula symbols while navigating gears.
- Scroll - M.M.A
Discussion of 'Doc the Destroyer', a unique fighting and adventure game for ZX Spectrum. The article covers controls, character customization, and game mechanics. Compatibility issues on different ZX Spectrum models are also addressed.
- Overview - M.M.A
The article provides a review of games for ZX Spectrum, including KOMANDO 2, WRESTLING SUPERSTARS, TAG TEAM WRESTLING, and CAPTAIN PLANET. It highlights the features, graphics, and gameplay of each game, noting both strengths and weaknesses. The review concludes with recommendations and comparisons to other platforms and games.
- Overview
Overview of various ZX Spectrum games, highlighting their unique features, gameplay mechanics, and design elements. Includes critique on sound effects, graphics, and technical issues. Discusses games like 'Stryker in the Crypts of Trogan', 'Phileas Fogg's Balloon Battles', and 'Survival'.
- Overview - Alex Noman
The article reviews games for the ZX Spectrum, including BOOVIE, MOTOR MASSACRE, SOCCER PINBALL, and HUXLEY PIG 1 & 2. Each game is detailed in terms of gameplay, graphics, and unique features. The discussion includes comparisons to other games and highlights specific technical aspects.
- Review
A review of various games, including Little Computer People and Lost Caves, highlighting their features and versions. It also discusses 75Occ Grand Prix by Codemasters with its limitations. The article provides insights into game mechanics and versions.
- Review
Detailed review of various assemblers like Alasm 3.8, TASM 4.12, and others, highlighting their features and shortcomings.
- About Everything
Announcement of the creation of the SamZxNet network in Samara and the challenges of setting it up with HAYES modems. Explanation of the modems' power requirements and potential difficulties. Invitation for technical advice from experienced readers.
- About Everything
Description of travel to ENLIGHT'97 and meeting various demoscene participants. Observations of event organization and issues. Insights into participant experiences and scene discussions.
- About Everything
Report on the second day of ENLIGHT'97: events, challenges, and reflections. Describes voting results and organizational difficulties. Highlights future prospects for Spectrum demo parties.
- About Everything
The article features reader feedback on Oberon #04, critiquing design and content choices and discussing issues with software protection and game enhancements.
- About Everything
Discussion of the adventure game KAYLETH with gameplay tips and advice. Includes a game dictionary and suggestions from the author and their team. Calls for a local artist for future RPG development.
- About Everything
Reflection on the closure of the 'ZX-REVIEW' magazine and the adaptation of its article for 'Oberon'. Discussion on the development of ultra-short boot loaders. Optimization techniques for writing one-sector boot loaders on ZX Spectrum.
- About Everything
Exploration of amateur contributions to electronics, music, and computing history, highlighting figures like Faraday and Babbage. The evolution from handmade instruments to personal computers. Discussion on jazz, blues, and rock'n'roll's informal origins.
- About Everything
The story of Lieutenant Edward Roberts' journey from radio kits to creating the first PC, the Altair 8800, overcoming skepticism and challenges.
- About Everything
The article explores the rise and evolution of the computer industry, highlighting the transformation from passionate hobbyists to corporate dominance by giants like IBM and Microsoft.
- About Everything
An exploration of Sir Clive Sinclair's project after selling the Sinclair brand, detailing the features of the Cambridge Computers Z88 laptop.
- About Everything
Discussion of software market problems in 1997 for ZX Spectrum, highlighting lack of new software and user reluctance to pay.
- Announcement - M.M.A
Announcement of 'Black Raven' game by V. Mednonogov, focusing on gameplay, technical challenges, and upcoming features.
- Announcement
Discussion of the decline in ZX Spectrum development, reviews of new games and utilities, and announcements of future projects.
- Educational Program
The article provides an overview of FidoNet, a non-commercial computer network often considered the predecessor of the Internet, detailing its origins, growth, and unique cultural aspects.
- Hardware
Instructions for connecting the 'ALEGRO' modem to computers with normal port #FF, detailing hardware modifications required for proper signal handling.
- Hardware
Connecting Hayes-compatible modems to ZX Spectrum, focusing on Scorpion and Pentagon models, detailing hardware modifications. Specific instructions for internal port blocking and signal alignment provided. Step-by-step process and technical intricacies explained.
- Hardware
Discussion of the transition from 5.25' to 3.5' floppy disks for ZX Spectrum, including installation issues and solutions for compatibility with existing software.
- Let's Feast
A satirical story about a Rabbit who lost his house to a cunning Fox and how a Rooster helped him reclaim it.
- Let's Gourmet
A humorous tale about Malysh and Karlson's adventures with technology, drawing parallels between computers and everyday life, culminating in a comic mishap with an AMIGA computer.
- Advertising
Article discusses free advertising policy of Oberon, catalog of programs and hardware for ZX Spectrum, and adventure game engagement.
- Advertisement - Kano
Promotional campaign by Magic Soft and RPSG in Russia for Amiga multimedia computers, offering exhibitions, sales, and consultations. They highlight Amiga's advantages over other systems, describe various models, and provide price lists. Collaboration with 'Computers for Population' for distribution and services.
