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