<    

USB Connectors

The USB ports use USB Type A connectors, which have four pins each. Two of the pins are used for power and two for data. Figure 3-1 is an illustration of a Type A port; Table 3-1 shows the signals and pin assignments.

Figure 1   USB Type A port and pins


Table 1   Signals on the USB port

Pin

Signal name

Description

1 VCC +5 VDC
2 D- Data -
3 D+ Data +
4 GND Ground

The iMac provides 5-volt power to the USB ports. The maximum current available is 500 mA on each port (1 A total).

The USB ports support both low-speed and high-speed data transfers, at up to 1.5 Mbits per second and 12 Mbits per second, respectively. High-speed operation requires the use of shielded cables.

The iMac comes with version 1.4.3 of the Macintosh USB system software, which supports all four data transfer types defined in the USB specification.


© 2000 Apple Computer, Inc. – (Last Updated 01 Aug 00)