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PC to Panasonic TV VGA connection


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Old 10-08-2009, 17:41
Snowsride
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I have a 3 month old Panasonic TX-37LZD800 TV to which I want to connect my PC using a VGA splitter.

There are 2 types of VGA connectors for sale both with 15 pins but one is 'fully wired' and the other is not wired on the number 9 pin.

Would the PC and the TV ignore the wired pin number 9 if it wasn't needed or must I get the correct type of cable? I ask because I can't find out from Panasonic which type of cable is needed.

Thanks for any help.
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Old 10-08-2009, 18:04
hardeep
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I didn't know you could get fully wired VGA cables

Anyhow if you check the back of the Panny's manual you will find a wiring diagram for all the connections - scart, HDMI and VGA.

In the manual for my Panasonic plasma it shows that pin 9, (and pin 4,) aren't used - "NC (not connected)" - I'd be pretty sure that the same applies to your LCD.

The pc and tv would ignore the wire any way because even though the pins are connected in the cable the pin on the TV isn't connected to anything.
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Old 10-08-2009, 18:11
LCDMAN
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Pin 9 was never originally connected, but used later to allow an optional +5V output from graphics cards as part of the DDC implementation. I'm fairly sure in your application it won't matter either way if pin 9 is wired or not.

VESA DDC

VESA Display Data Channel is a method for integrating digital interface to VGA connector so as to enable the monitor and graphics card to communicate. There are two different levels of DDC: DDC1 and DDC2.

VGA DDC1
DDC1 allows the monitor to tell its parameters to the computer. The following VGA card connector pins have to be changed to allow DDC1 functions:

VGA pin new function
9 Optional +5V output from graphics card
12 Data from display
14 Standard vertical sync signal which works also as data clock
15 Monitor ID3
When the VGA graphics card detects data on data-line it starts to read the data coming from the monitor synchronous to vertical sync pulse. Vertical sync pulse frequency can be increased up to 25 KHz for the time of the data transfer if a DDC1 compliant monitor is found (be sure not to send those high frequencies to non DDC1 monitors!).

VGA DDC2
DDC2 allows bidirectional communication: monitor can tell its parameters and the computer can adjust monitor settings. The bidirectional data bus is a synchronous data bus similar to Access Bus and is based on I2C technology. The following pins on VGA pinout have to be changed to enable DDC2 to work:

VGA pin new function
9 Optional +5V output from graphics card
12 Bidirectional data line (SDA)
15 Data clock (SLC)
The signals in the data bus are standard I2C signals. The computer provides 15 kohm pullup for the SDA and SLC lines. Monitor must provide 47 kohm pull-up on SCLK line.
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Old 10-08-2009, 18:19
hardeep
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You live and learn.

So presumably that's how my laptop can automatically change its settiongs to match the resolution on a projector/whiteboard.
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Old 10-08-2009, 19:39
Snowsride
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Many thanks to all. I'll get a 15 pin fully wired to be on the safe side.
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