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Digital Monitor Connector

The connector for the digital video monitor is an Apple proprietary connector called the ADC (Apple display connector). It carries both digital and analog video signals as well as USB and control signals and power for an external monitor. Figure 3-4 shows the contact configuration; Table 3-6 and Table 3-7 list the signals and pin assignments.

The maximum current available from the 28-V supply for the external monitor is 4.0 A.

Figure 3-4 Apple display connector

Table 3-6 Digital signals on the Apple display connector

Pin	Signal name	Pin	Signal name
1	28-V Supply	16	TMDS Data1/3 Shield
2	28-V Supply	17	TMDS Data3-
3	LED	18	TMDS Data3+
4	TMDS Data0-	19	DDC CLock
5	TMDS Data0+	20	Clock Return
6	TMDS Data0/5 Shield	21	USB Data+
7	TMDS Data5-	22	USB Data-
8	TMDS Data5+	23	USB Return
9	DDC Data	24	TMDS Data2-
10	Vsync	25	TMDS Data2+
11	28-V Return	26	TMDS Data2/4 Shield
12	28-V Return	27	TMDS Data4-
13	Soft Power	28	TMDS Data4+
14	TMDS Data1-	29	Clock+
15	TMDS Data1+	30	Clock-

Table 3-7 Analog signals on the Apple display connector

Pin	Signal name
C1	Analog Blue Video
C2	Analog Green Video
C3	Analog Horizontal Sync
C4	Analog Red Video
C5	Analog RGB Return and DDC Return

The graphics data sent to the digital monitor use transition minimized differential signaling (TMDS). TMDS uses an encoding algorithm to convert bytes of graphics data into characters that are transition-minimized to reduce EMI with copper cables and DC-balanced for transmission over fiber optic cables. The TMDS algorithm also provides robust clock recovery for greater skew tolerance with longer cables or low cost short cables. For additional information about TMDS, see the references shown in Digital Visual Interface.