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USB Device Architecture and OS X Implementation

Yapay zekadan makale özeti

Device Types and Speeds: USB supports devices from keyboards to digital cameras
Version 1.1 offers 1.5 Mbps and 12 Mbps speeds
Version 2.0 adds 480 Mbps high-speed capability
Apple provides USB 2.0 ports on all new Macintosh computers
Device Architecture: USB devices consist of configurations, interfaces, and endpoints
Composite class devices appear as single device with multiple interfaces
Devices communicate through pipes between endpoints and host
Each endpoint has transfer type, maximum packet size, and direction
Transfer Types: Control transfers support configuration and status communication
Interrupt transfers handle small, limited-latency data transfers
Isochronous transfers provide periodic, continuous communication
Bulk transfers handle large-packet, non-periodic data transfers
OS X Implementation: USB devices represented by IOUSBDevice nub objects
Interface objects (IOUSBInterface) manage specific device functions
Applications must use correct interface version for OS X version
Low latency isochronous transfers available in version 1.9.2
USB 2.0 Changes: Divides 1-millisecond frames into 8 125-microsecond microframes
Maximum data transfer size increased to 3 KB
New functions for bandwidth management and endpoint control
EHCI hub provides coarser-grained error reporting than OHCI