Technical information

CHAPTER 3
Devices and Ports
52 External Monitors
adapter, this pin is connected to the VSYNC signal. If the adapter is not found,
the computer next checks to determine whether a DDC-type monitor is
connected. DDC is the interface that provides monitor ID signals for VGA and
SVGA monitors.
If the computer does not detect a DDC-capable monitor, it uses the Apple
monitor sense codes on the signals MONID(0–2) in Table 3-11. For a description
of the sense code system, developers should refer to Technote HW 30 - Sense
Lines. To find out how to obtain Apple Computer’s Technotes, see
“Supplemental Reference Documents” (page 12).
Table 3-11 Signals on the video connector
Pin Signal name Description
1 RED Red video signal
2 GREEN Green video signal
3 BLUE Blue video signal
4 MONID(0) Monitor ID signal 0
5 GND DDC return
6, 7, 8 AGND_VID Analog video ground
9 +5V_IO 5 V power for I/O device
10 GND HSYNC and VSYNC ground
11 VGA_ID VGA ID signal
12 MONID(2) Monitor ID signal 2
13 HSYNC Horizontal synchronization signal
14 VSYNC Vertical synchronization signal
15 MONID(1) Monitor ID signal 1