Nearly all modern PC graphics cards use the same 15 pin connector that the original IBM VGA card used. VGA=Video Graphics adapter or Video Graphics Array. Videotype: Analogue.
15 pin HIGHDENSITY D-SUB female connector at the videocard
Monitor ID detection pin assignments
4 11 12 ID2 ID0 ID1 n/c n/c n/c no monitor n/c n/c GND Mono monitor which does not support 1024x768 n/c GND n/c Color monitor which does not support 1024x768 GND GND n/c Color monitor which supports 1024x768GND means connected to ground
n/c means that the pin is not connected anywhere
This monitor type detection is becoming more and more obsolete nowadays. New plug-and-play monitors communicate with the computer according to VESA DDC standard.
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.
DDC1 allows the monitor to tell it’s parameters to the computer. The following VGA card connector pins have to be changed to allow DDC1 functions:
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 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!).
DDC2 allows bidirectional communication: monitor can tell it’s 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 have to be changed to enable DDC2 to work:
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.
15 pin HIGHDENSITY D-SUB male connector at the monitor cable