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EF9345 video

A look at the EF9345 video chip

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Just a collection of information about this chip and boards that use it.

The pixel clock is 8 or 16 MHz so the screen is squashed into 40µs of the 44µs PAL display time (just like the BBC Micro). The pixels are not exactly square, but that is only desirable in pixel graphics.

The Dutch Acorn Atom user group board combines the RGB outputs into a single monochromes composite video. It is documented in Acorn Atom News. This is online but the document scans are low resolution. Readable by humans but poor OCR.

A board by AMS Sales uses a 32K SRAM chip and the PAL video modulator copied from the BBC Micro. The modulator circuitry could be omitted and the RGB inputs buffered to 75 ohms impedance and fed to a TV's SCART socket.

Most television circuits would not have the bandwidth or phosphor-dot density to support 80-column text. A monitor would be a wiser option, if you can get one.

The EF9345 was used in the very popular French machine, the Minitel. I can't find original schematics for it but http://vtrm.net/elec/minitel/en has reverse-engineered the circuit and added modern peripherals. The site says the video clock was 14.318 MHz, the data sheet specifies 16 MHz so perhaps the CRT ran proportionately slower (44.74 Hz?). The processor was an 8052 microcontroller, not much power but enough to be a simple terminal for telephone-line based data services.

F101-V-2x-cvideo_schematic.jpg

A board that uses a 32K SRAM for the video memory, and the PAL colour modulator from the BBC Micro. Could be simplified by omitting the PAL modulator and just having RGB output.

JPEG Image - 269.92 kB - 10/30/2021 at 14:52

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EF9345_datasheet.pdf

EF9345 datasheet.

Adobe Portable Document Format - 743.60 kB - 10/30/2021 at 14:07

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  • Acorn Atom News 1992 Number 3, The 80-column starter pack

    Keith • 10/30/2021 at 15:20 • 0 comments

    HET 80 KOLOMMEN STARTPAKKET

    verzameld door Roland Leurs 

    Steeds meer en meer mensen komen in het bezit van de 80 koloms clubkaart. Echter in de loop der jaren zijn zoveel programma’s en met hun vele vervolgversies geschreven, dat een beginnende 80 kolomskaart niet weet waar te zoeken.

    Omdat iemand mij vroeg oa wat software bij elkaar te piaatsen, heb ik dat gedaan. Aangezien het een kleine moeite is om dat even in Atom Nieuws te vermelden, volgt hier een opsomming van enkele programma’s voor de 80 koloms clubkaart: 

    80 KOLOMSSOFT DRIVE E QUAL 

A:  EDIT80         IM.CODE        INFOM80 

D:  DC             DC.INIT        DECAT 
    DISKCAT        PC-SORT        FCAT1
    PCAT2          SETCAT 

F:  8X8ITAL        BBC            LCD 
    SLANT

V:  EXT-3.4       JVDUO.O         VDU-3.4 

X:  ACCENT        EIKEL           KLEUR 
    LOGO          NEDER           STROKE

    De programma’s EDITAO en INFOM80O zijn de sourcefiles van de tekstverwerker en database; Jan Bronzwaer beschreef deze programma’s in AN7.1 blz 32 en AN6.3 blz 50.

    Diskcat is een uitgebreide 80 kolomsversie van dit bekende schijven catalogus progamma. Het pakket wordt gestart met ERUN DC. Er wordt naar de naam van de catalog-tije gevraagd. Dit geeft de mogelijkheid om met verschillende bestanden te werken, voor diegenen die meer dan 54 diskettes hebben.

    U dient bij de eerste opstart met DC.INIT een catalog-file aan te maken. Uiteraard is het mogelijk om catalog-files van oudere Diskcat versies te gebruiken, De “originele” catalog-file heet FCAT.

    De pragramma’s onder de qualifier X zijn een aantal demo programma’s voor VDUS.4 en de fonts (qual F) zijn aen aantal daor mij gemaakte karaktersets, Deze fonts werken alleen in VDS.4.

    Alles bij elkaar toch al wat software om een nieuwe aanwinst direct te kunnen gebruiken en bekijken. Succes ermee!

    Met de vriendelijke groeten van Roland.

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64rulez at gmail wrote 03/11/2022 at 21:13 • point

Very nice to see someone wondering to make a serious hacks to the Minitel and around the EF9345. I'm myself fighting, with poor electronics knowedge, to get "high quality" display of the Minitel on a big screen (30' or more) and/or be able to capture this in MP4. I've been able to get "mostly correct" results (detail in this post : https://forum.museeminitel.fr/t/minitel-sortie-rgb/191/15) but I'm still far from the quality I would expect. Any comments welcome, specially in comparison with what you can get with your SCART solution based uppon 74ACT241.

  Are you sure? yes | no

Keith wrote 03/11/2022 at 22:07 • point

I'd be inclined to intercept the data going from the 8052 to the EF9345, then render the screen in software on a Raspberry Pi, which can drive a modern TV directly. Then again, you might as well get the Pi emulating a Minitel terminal to some internet-based server.

  Are you sure? yes | no

64rulez at gmail wrote 03/11/2022 at 22:27 • point

Hum ... That's another approach. I know that it exists a MAME emulation of the EF9345 (for the VG5000 emulator), but, AFAIK, it's not exempt of bugs (plus no support for EF9340/41 and uncertain support for the EF9347). The solution to fully emulate a Minitel for a RPi (or whatever) is out of the scope of this project in order to be certain to render pictures exactly as a real terminal would. Currently, I don't have any 74ACT241 sourced yet to test. If you have a look at the video available at the end of my post, how would you compare your results with mine ?

  Are you sure? yes | no

zpekic wrote 10/30/2021 at 19:07 • point

Great to see this chip being brought back to life! I was playing a bit with it back in the late 80ies (I believe based on Elektor, or maybe mc German computer mag?) and still have a few somewhere, it would be great to see them working. Maybe with a Propeller like I did for TMS9918 / 9958. 

  Are you sure? yes | no

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