PATHHardware Documentation > USB Devices > Mac OS USB DDK API Reference

USB Data Transfer Types Supported

There are four data transfer types defined by the USB specification. They are

• Bulk transfers which offer guaranteed delivery of data. This may include retrying transmissions at the hardware level. Bulk data transactions are best suited for printers, scanners, modems, and devices that require accurate delivery of data with relaxed timing constraints.
• Interrupt transfers, which allow a device to signal the host. Interrupt data transactions do not use up CPU cycles unless the device has data ready. Interrupt transactions are used for HID class devices like keyboards, mice, joysticks, as well as devices that want to report status changes, such as serial or parallel adaptors and modems.
• Isochronous transfers for one time delivery of data. Isochronous data transactions are best suited for audio or video data streams.
• Control transfers for device configuration and initialization.

Version 1.0 of the Mac OS USB software provides functions that support only control, bulk, and interrupt transfer types. Version 1.1 supports control, bulk, interrupt, and isochronous transfers types.

Previous | Back Up One Level | Next |