Tuesday 28 May, 2024
Welcome to RISCOS.org
Jump to 
Search Articles 
Search for Software 

Old monitor plugs

Taxan/Kaga RGB vision I/II/III (and others)

From the taxan/kaga RGB vision I, II, III manual (thanks to Joost for the scans):

These also apply to other monitors:

Note that the pin numbers refer to the actual numbers printed on the plugs and connectors, so don't worry about inside/outside view when soldering.

Connecting to a BBC computer

Using the TTL input (8 pin DIN plug): connect the BBC's sync (=composite sync) to the HSYNC/COMPOSITE SYNC, 0V to ground, R/G/B to R/G/B, and 0V to I/XRGB8 (intensity).

   BBC: 6 pin DIN             monitor: 8 pin DIN
   ---                        ------------------
   0 V      (5) ------------- (6,5) ground, intensity
   red      (1) ------------- (2) red input
   green    (2) ------------- (3) green input
   blue     (3) ------------- (4) blue input
   sync     (4) ------------- (7) horizontal sync/composite sync
   5 V      (6) X
                            X (8) vertical sync

Using the TTL/linear input (EIAJ plug): connect the BBC's sync (=composite sync) to the HSYNC/COMPOSITE SYNC, 0V to ground, R/G/B to R/G/B.

Eizo 8060s

Does anyone have the connection details? (voltage levels/pinouts for TTL & analog RGB modes)

BBC computer to SCART: cable wiring:

Pin numbers on the connectors are in brackets. The pin numbers are printed on the plugs (not always on the SCART plug though).
Scart connector:
   \  20                           2   |
    \  |  |  |  |  |  |  |  |  |  |    |
     \                                 | 21
      |                                |
      |  |  |  |  |  |  |  |  |  |  |  |
      | 19                           1 |
21 = shielding
   BBC                        SCART
   ---                        --
   0 V      (5) ------------- ground (blue), ground (green), ground (red),
                              ground (blanking), ground (RGB switching control)
   red      (1) -- Rrgb ----- red input (15)
   green    (2) -- Rrgb ----- green input (11)
   blue     (3) -- Rrgb ----- blue input (7)
   sync     (4) -- 330 ohm -- video input (composite) (20)
   5 V      (6) -- 82 ohm --- RGB switching control (16)

Rrgb is e.g. 330 ohm.


On the SCART side, the above inputs always have 75 ohm impedance. This means one can easily lower voltage outputs to those required by the SCART device by placing a resistor before the SCART input, thus creating a voltage divider.

The BBC computer outputs are:

   R,G,B:                 TTL (ca. 3.6V for 'on'), with 68 Ohm impedance.
   sync:                  >= 4V

SCART input ranges are:

   R,G,B:                 0 - 0.7 V
   video input:           0 - 1 V
   RGB switching control: high (1-3V) for RGB, low (0-0.4V) for composite

We want to use the BBC's (TTL) RGB signals, so 'RGB switching control' should get in the range of 1-3 V. We can use the 5V signal from the BBC for this, using a resistor of say 82 Ohm to give ca. 2.5 V.

The sync signal from the BBC is more than 4 V (5 V peaks?); 330 Ohm is large enough to reduce it to less than 1 V (a much larger resistor also works fine).

The RGB output from the BBC is TTL (0 V is off, >=3.5 V is on; the actual value in this case is around 3.6V) which we can reduce using resistors of at least ca. 330 Ohm.

(3.6V/0.7V=5.14, so total resistance should be 4.14*75=311 Ohm at the very minimum; minus the 68 Ohm for the outputs gives a Rrgb of 243 Ohm. However, this gives the maximum intensity for the computer image, which is almost certainly not what you want and you'll have to turn down the brightness each time you use the computer on the TV)

The resistors are best placed inside the SCART connector where there's plenty of room for them.

NOTE: Some people suggest using voltage level convertor ICs to get around any reflections that accur at the places where resistance changes. I've used the simple method on various BBCs and various TVs without seeing any of the effects of reflections like ghosting/blurred pixels. So I would not bother with it. If your TV set gives problems, you may want to try using a voltage level convertor IC.

There is a whole host of extra information available at Wouter's BBC micro scans and pictures

Add a comment to this article

If you wish to add a comment to this article, please use the form below. Please note that by submitting comments using this form you are allowing all of the information submitted to be visible on this website. Your comment will be published immediately, so please proof-read before you add. Any comments deemed to be abusive or irrelevant to the topic of the article may be removed without warning.

Posted by: (optional)

Email or web site: (optional, emails will be mangled to avoid spambots)

Comments: (maximum length 2000 characters)

If you would like to add a URL to another site, please enter the address (without http://) inside square brackets. Use an optional closing curly bracket to add a description. eg. to link to http://www.vigay.com enter [www.vigay.com}Vigay.com]

To prevent spambots, please re-enter the following code:

Email Email this page to a friend

 Last edit: 10th Apr 2016 at 4:55pm (2970 days ago)

Bookmark with:What are these?
delicious Deliciousdigg Diggreddit redditfacebook Facebookstumbleupon StumbleUpon

RSS Feed 

Valid HTML 4.01!
Valid CSS!
Best viewed with a cup of tea Crafted by RISC OS