Computer

Does anyone know how the VGA video feature connector operates? I would like to know which of the pins are inputs, which are outputs, and which are bidirectional (if any - and how the direction is selected).

I have found a pinout for the connector:

Video Feature Connector Pinouts.

Pin     Name   Function 1       PD0    Dac Pixel data bit 0 2       PD1                   bit 1 3       PD2                   bit 2 4       PD3                       3 5       PD4                       4 6       PD5                       5 7       PD6                       6 8       PD7                       7 9       -      Dac Clock 10      -      Dac Blanking 11      -      Horizontal Sync 12      -      Vertical Sync 13      -      Ground  14      -      Ground 15      -      Ground 16      -      Ground 17      -      Select Internal Video 18      -      Select Internal Sync 19      -      Select Internal Dot Clock 20      -      Not Used 21      -      Ground 22      -      Ground 23      -      Ground 24      -      Ground 25      -      Not Used 26      -      Not Used 

And I assume that pins 1 - 12 are outputs, and 17 - 19 are inputs. Is this correct?

The reason is this - I have a Rombo Media Pro+ video digitising card. It chroma keys its output into the vga monitor signal. However, although it is supposed to work with an ET-4000 with Hi-colour RAMDAC, the colours on screen behave as if the top 2 bits of colour information are missing, and red, green, blue signals are swapped around. Rombo has suggested that this may be due to insufficient buffering on the feature connector outputs, and is happy to sell me a buffer device for 50 pounds. I would rather save about 45 pounds, and build my own. I assume it would require (for example) a 74F244 buffer IC (or two).

Does anyone know how the VGA video feature connector operates? I would like to know which of the pins are inputs, which are outputs, and which are bidirectional (if any - and how the direction is selected).

I have found a pinout for the connector:

Video Feature Connector Pinouts.

Pin     Name   Function 1       PD0    Dac Pixel data bit 0 2       PD1                   bit 1 3       PD2                   bit 2 4       PD3                       3 5       PD4                       4 6       PD5                       5 7       PD6                       6 8       PD7                       7 9       -      Dac Clock 10      -      Dac Blanking 11      -      Horizontal Sync 12      -      Vertical Sync 13      -      Ground  14      -      Ground 15      -      Ground 16      -      Ground 17      -      Select Internal Video 18      -      Select Internal Sync 19      -      Select Internal Dot Clock 20      -      Not Used 21      -      Ground 22      -      Ground 23      -      Ground 24      -      Ground 25      -      Not Used 26      -      Not Used 

And I assume that pins 1 - 12 are outputs, and 17 - 19 are inputs. Is this correct?

The reason is this - I have a Rombo Media Pro+ video digitising card. It chroma keys its output into the vga monitor signal. However, although it is supposed to work with an ET-4000 with Hi-colour RAMDAC, the colours on screen behave as if the top 2 bits of colour information are missing, and red, green, blue signals are swapped around. Rombo has suggested that this may be due to insufficient buffering on the feature connector outputs, and is happy to sell me a buffer device for 50 pounds. I would rather save about 45 pounds, and build my own. I assume it would require (for example) a 74F244 buffer IC (or two).

VGA frequencies in different modes

From: steveq@syd.dms.CSIRO.AU (Stephen Quigg) Newsgroups: sci.electronics Subject: Re: VGA startup board/monitor sync? Date: 14 May 91 23:06:07 GMT Organization: CSIRO Maths and Stats & Applied Physics, Sydney, Australia 

The VGA board tells the monitor what to expect by the polarity of the horiz. and vert. sync signals. Here's what an NEC MultiSync 2A sets up to.

Vert Res.      Horiz Freq    H Sync    Vert Freq    V Sync                             Polarity               Polarity  350 lines      31.5 kHz      pos       70.07 Hz     neg 400 lines      31.5 kHz      neg       70.07 Hz     pos 480 lines      31.5 kHz      neg       59.95 Hz     neg 600 lines      35.2 kHz      pos       56.24 Hz     pos 

Your problem is probably one of the following; 1. You are trying a mode your monitor won't support. 2. Your monitor is out of adjustment. 3. Your monitor is faulty. Possibly, the card or monitor is not "playing the rules", eg monitor expects one set of sync rates according to the sync polarities, and the card is sending out another (unlikely but...)

VGA monitor ID signals

From: Jay_R_Keller@cup.portal.com Newsgroups: sci.electronics Subject: Re: VGA monitors Date: 22 May 91 01:49:05 GMT Organization: The Portal System (TM) 

Mike Diack asked about VGA monitors.

Mike, I don't know if this is related to your problem or not, but IBM monitors have 3 pins dedicated to a "monitor ID" code, which is available to the VGA (or 8514/A or XGA) card, and also to the software. OS/2 uses it, for example, to automatically install the correct display support. The code:

PIN 4      PIN 11      PIN 12           Meaning  n/c        n/c         n/c         No monitor attached  n/c        n/c         GND         Mono monitor with no support for 1024x768  n/c        GND         n/c         Color monitor with no support for 1024x768  GND        GND         n/c         Color monitor with support for 1024x768 

Maybe your projector is not providing the code to tell the VGA that it is there. If so, you can try modifying the plug.

DISCLAIMER: I know this works for some Sony monitors, which support 1024x768 but don't provide the proper code to the PS/2, so they come up in 640x480. By changing the plug, the system sees the monitor as high-res-capable, and configures itself for 1024x768. Whether grounding pins in your plug will your projector, however, I can't say (although I doubt it).

Good luck.

VGA frequencies in different modes

From: steveq@syd.dms.CSIRO.AU (Stephen Quigg) Newsgroups: sci.electronics Subject: Re: VGA startup board/monitor sync? Date: 14 May 91 23:06:07 GMT Organization: CSIRO Maths and Stats & Applied Physics, Sydney, Australia 

The VGA board tells the monitor what to expect by the polarity of the horiz. and vert. sync signals. Here's what an NEC MultiSync 2A sets up to.

Vert Res.      Horiz Freq    H Sync    Vert Freq    V Sync                             Polarity               Polarity  350 lines      31.5 kHz      pos       70.07 Hz     neg 400 lines      31.5 kHz      neg       70.07 Hz     pos 480 lines      31.5 kHz      neg       59.95 Hz     neg 600 lines      35.2 kHz      pos       56.24 Hz     pos 

Your problem is probably one of the following; 1. You are trying a mode your monitor won't support. 2. Your monitor is out of adjustment. 3. Your monitor is faulty. Possibly, the card or monitor is not "playing the rules", eg monitor expects one set of sync rates according to the sync polarities, and the card is sending out another (unlikely but...)

VGA monitor ID signals

From: Jay_R_Keller@cup.portal.com Newsgroups: sci.electronics Subject: Re: VGA monitors Date: 22 May 91 01:49:05 GMT Organization: The Portal System (TM) 

Mike Diack asked about VGA monitors.

Mike, I don't know if this is related to your problem or not, but IBM monitors have 3 pins dedicated to a "monitor ID" code, which is available to the VGA (or 8514/A or XGA) card, and also to the software. OS/2 uses it, for example, to automatically install the correct display support. The code:

PIN 4      PIN 11      PIN 12           Meaning  n/c        n/c         n/c         No monitor attached  n/c        n/c         GND         Mono monitor with no support for 1024x768  n/c        GND         n/c         Color monitor with no support for 1024x768  GND        GND         n/c         Color monitor with support for 1024x768 

Maybe your projector is not providing the code to tell the VGA that it is there. If so, you can try modifying the plug.

DISCLAIMER: I know this works for some Sony monitors, which support 1024x768 but don't provide the proper code to the PS/2, so they come up in 640x480. By changing the plug, the system sees the monitor as high-res-capable, and configures itself for 1024x768. Whether grounding pins in your plug will your projector, however, I can't say (although I doubt it).

Good luck.