Full Speed USB
Specification
- USB Full Speed mode was introduced in 1996 with the USB v1.0 specification (later revised to USB 1.1 1998)
- Maximum theoretical bandwidth is 1.2 Mbits/sec
- Uses four data lines - Power (5 V), ground, and two data lines (D+ and D-)
- Half-Duplex differential signaling on D+ and D-
- Uses the traditional (i.e. defined before USB 3.0) USB connectors
Enumeration
Full Speed devices announce to a host that they are ready to be enumerated by asserting 5 V on D+ through a 1.5 KΩ pull-up resistor.
Frame Size and Transfer Types
FULL SPEED Frame size: 1 ms
| Supported Transfer Types |
Maximum Size of Transfer |
Transfers per frame |
Maximum Theoretical Throughput |
| Control | 64 bytes | 1 | 64 kbytes/s |
| Interrupt | 64 bytes | 1 | 64 kbytes/s |
| Bulk | 64 bytes | Up to 19 | 1.2 Mbytes/s |
| Isochronous | 1023 bytes | 1 | 1023 kbytes/s |
USB Bus States and Signal Levels
| FS USB Bus States |
Bus Levels |
|---|---|
| Differential "1" | D+ high, D- low |
| Differential "0" | D+ low, D- high |
| Single Ended 0 (SE0) | D+ low, D- low |
| Single Ended 1 (SE1) | D+ high, D- high Invalid condition! |
| Data J state | Differential "1" |
| Data K State | Differential "0" |
| Idle | Data J |
| Resume | Data K |
| Start of Packet (SOP) | Switches from Idle to Data K |
| End of Packet (EOP) | SE0 for two bits, followed by Data J for one bit |
| Disconnect | SE0 >= 2 μs |
| Connect | Idle for 2.5 μs |
| Reset | SE0 >= 2 μs |