
Software – General Concepts
The General USB Process
The Enumeration Process:What happens when a device is connected?
5.The available bandwidth is then divided into frames, and the host controls those frames which contain 1,500 bytes. Every millisecond a new frame begins. Within the frame, slots are reserved for isochronous and interrupt devices (up to 90%) so that they are guaranteed the bandwidth they need. Bulk and control transfers use whatever space is left.
|
|
|
|
|
|
|
|
|
| TM |
|
|
|
|
|
|
| Frame |
|
|
|
|
|
| |
Transfer 1 |
|
|
| Transfer 2 |
|
|
| Transfer 3 | ||||
Transaction | Transaction 1 | Transaction 2 | Transaction 3 | Transaction 1 | ||||||||
Start of Frame | Packet 1 | Packet 2 | Packet 3 | Packet 1 | Packet 2 | Packet 3 | Packet 1 | Packet 2 | Packet 3 | Packet 1 | Packet 2 | Packet 3 |
|
|
|
| 1500 bytes / 1 Ms |
|
|
|
|
|
|