USB 2.0
Datasheet |
|
|
|
8.2.1.29 | Register F8h: Boost_4:0 | ||
|
|
|
|
BIT |
|
|
|
NUMBER | BIT NAME |
| DESCRIPTION |
|
|
|
|
7:6 | BOOST_IOUT_4 |
| USB electrical signaling drive strength Boost Bit for Downstream Port ‘4’. |
|
|
| ‘00’ = Normal electrical drive strength = No boost |
|
|
| ‘01’ = Elevated electrical drive strength = Low (~4% boost) |
|
|
| ‘10’ = Elevated electrical drive strength = Medium (~ 8% boost) |
|
|
| ‘11’ = Elevated electrical drive strength = High (~12% boost) |
|
|
|
|
5:4 | BOOST_IOUT_3 |
| USB electrical signaling drive strength Boost Bit for Downstream Port ‘3’. |
|
|
| ‘00’ = Normal electrical drive strength = No boost |
|
|
| ‘01’ = Elevated electrical drive strength = Low (~4% boost) |
|
|
| ‘10’ = Elevated electrical drive strength = Medium (~ 8% boost) |
|
|
| ‘11’ = Elevated electrical drive strength = High (~12% boost) |
|
|
|
|
3:2 | BOOST_IOUT_2 |
| USB electrical signaling drive strength Boost Bit for Downstream Port ‘2’. |
|
|
| ‘00’ = Normal electrical drive strength = No boost |
|
|
| ‘01’ = Elevated electrical drive strength = Low (~4% boost) |
|
|
| ‘10’ = Elevated electrical drive strength = Medium (~ 8% boost) |
|
|
| ‘11’ = Elevated electrical drive strength = High (~12% boost) |
|
|
|
|
1:0 | BOOST_IOUT_1 |
| USB electrical signaling drive strength Boost Bit for Downstream Port ‘1’. |
|
|
| ‘00’ = Normal electrical drive strength = No boost |
|
|
| ‘01’ = Elevated electrical drive strength = Low (~4% boost) |
|
|
| ‘10’ = Elevated electrical drive strength = Medium (~ 8% boost) |
|
|
| ‘11’ = Elevated electrical drive strength = High (~12% boost) |
|
|
| |
| Note: “Boost” could result in | ||
| specific implementation issues require additional signal boosting to correct for degraded USB | ||
| signalling levels. |
| |
8.2.1.30Register FAh: Port Swap
BIT |
|
|
NUMBER | BIT NAME | DESCRIPTION |
|
|
|
7:0 | PRTSP | Port Swap: Swaps the Upstream and Downstream USB DP and DM Pins for |
|
| ease of board routing to devices and connectors. |
|
| ‘0’ = USB D+ functionality is associated with the DP pin and D- functionality |
|
| is associated with the DM pin. |
|
| ‘1’ = USB D+ functionality is associated with the DM pin and D- functionality |
|
| is associated with the DP pin. |
|
| Bit 7= Controls Port 7 |
|
| Bit 6= Controls Port 6 |
|
| Bit 5= Controls Port 5 |
|
| Bit 4= Controls Port 4 |
|
| Bit 3= Controls Port 3 |
|
| Bit 2= Controls Port 2 |
|
| Bit 1= Controls Port 1 |
|
| Bit 0= When this bit is ‘1’, the upstream port DP/DM is swapped. |
|
|
|
SMSC USB251x | 47 | Revision 1.0 |
DATASHEET