usbuniversalserialbus(編輯修改稿)
2025-08-13 18:45 本頁面
【文章內(nèi)容簡介】 e pin Name Descryption 1 Vcc +5 Vdc 2 D Data 3 D+ Data+ 4 GND Ground University of Tehran 13 Throughput ? Low speed – Mbps ? Full speed – 12 Mbps ? High speed (in USB ) – 480 Mbps ? Dynamic mode switching ? Clock encoding scheme: NRZI (Non Return to Zero Invert) University of Tehran 14 Power Distribution ? Devices: – Buspowered devices – Selfpowered devices ? Power management – Host based – Power events: 187。 Suspend 187。 Resume University of Tehran 15 Bus Protocol ? Polled bus ? Data transfers initiated only by host controller ? Three packets: – Token packet 187。 Type 187。 Direction 187。 Address 187。 End point number – Data packet – Handshake packet 187。 ACK 187。 NAK University of Tehran 16 Transfer Model ? Pipe – Stream pipes 187。 No USB standard format – Message pipes 187。 USB format ? Request ? Data ? Status ? End point zero – Default control pipe – Always exists University of Tehran 17 Data Flow Types ? Control Transfers: – Used to configure a device at attach time and can be used for other devicespecific purposes, including control of other pipes on the device. ? Bulk Data Transfers: – Generated or consumed in relatively large and bursty quantities. ? Interrupt Data Transfers: – Used for characters or coordinates with humanperceptible echo or feedback response characteristics. ? Isochronous Data Transfers: – Occupy a prenegotiated amount of USB bandwidth with a prenegotiated delivery latency. (Also called streaming real time transfers). University of Tehran 18 USB Devices ? All have endpoint zero ? Hub ? Function ? Compound University of Tehran 19 Typical Configuration University of Tehran 20 Host Responsibility ? Detecting the attachment and removal of USB devices ? Managing control flow between the host and USB devices ? Managing data flow between the host and USB devices ? Collecting status and activity statistics ? Providing power to attached USB devices. University of Tehran 21 Implementer Viewpoints ? USB Physical Device: A piece of
環(huán)評(píng)公示相關(guān)推薦
鄂ICP備17016276號(hào)-1