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Mac OS Software for USB Devices

The software that supports USB devices in the Mac OS environment includes a USB Interface Module (UIM), a USB Manager, a USB Services Library (USL), and USB class drivers.

• The UIM, pronounced whim, communicates with the USB controller hardware and provides a hardware abstraction layer for the USL and USB Manager.
• The USB Manager is the API provided to the Mac OS, or extensions that need information related to the USB.
• The USL is the API that USB device drivers use to add device functionality to the USB on Macintosh computers. The API is defined in the USB.h file and USB Services Library Reference
• Device class drivers in version 1. 0 of the Macintosh USB system software include a USB composite device class driver to support USB HIDs, such as keyboards and mice, and a hub class driver to support hubs attached to the USB.

The Mac OS USB system software components are available as system extensions for Macintosh systems that do not include built-in USB ports. This generally applies to Macintosh computers that have USB ports on PCI cards. Macintosh computers that have USB ports designed into the main logic board, like the iMac computer, have all of the USB software components, excluding the class drivers, in the Macintosh system ROM.

Figure 3-1 shows the components that make up the USB software architecture on the Macintosh computer. Release version 1.0 of the Macintosh USB software provides only class driver support for a USB keyboard, mouse, and hub.

Figure 3-1 USB architecture

USB Software Presence and Version Attributes

USB Interface Module (UIM)

USB Manager

Hub Driver

USB Class Drivers

USB Services Library (USL)

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