Graphics know-how
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ELSA GLADIAC
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30
EN
DDC2B
A bi-directional data channel based on the I
2
C access-bus protocol is used for
the communication between monitor and graphics board. In the case of a
standard IBM VGA compatible 15-pin monitor connector, pin 12 (formerly
used as monitor ID bit 1) is used for data transmission (SDA), and the pin 15
(formerly used as monitor ID bit 3) is used as transmission clock (SCL). The
graphics board can request the short EDID information (see DDC1) as well as
the more comprehensive VDIF information (VESA Display Identification File).
DDC2AB
With DDC2AB additional to DDC2B, the computer can send commands for
controlling the monitor, e.g. for adjusting the screen position or the
brightness (similar to ACCESS bus). Modern monitors and graphics boards no
longer use this standard.
The pin assignment of the VGA D-shell socket can be found in the chapter
'Technical data'.
21663_DE_0300.book Seite 30 Montag, 10. April 2000 12:22 12
