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Datasheet
8.4SE0 Handling
For FS operation, IDLE is a J state on the bus. SE0 is used as part of the EOP or to indicate reset. When asserted in an EOP, SE0 is never asserted for more than 2 bit times. The assertion of SE0 for more than 2.5us is interpreted as a reset by the device operating in FS mode.
For HS operation, IDLE is a SE0 state on the bus. SE0 is also used to reset a HS device. A HS device cannot use the 2.5us assertion of SE0 (as defined for FS operation) to indicate reset since the bus is often in this state between packets. If no bus activity (IDLE) is detected for more than 3ms, a HS device must determine whether the downstream facing port is signaling a suspend or a reset. The following section details how this determination is made. If a reset is signaled, the HS device will then initiate the HS Detection Handshake protocol.
8.5Reset Detection
If a device in HS mode detects bus inactivity for more than 3ms (T1), it reverts to FS mode. This enables the FS
Figure 8.1 Reset Timing Behavior (HS Mode)
Table 8.4 Reset Timing Values (HS Mode)
TIMING |
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PARAMETER | DESCRIPTION | VALUE |
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HS Reset T0 | Bus activity ceases, signaling either a reset | 0 (reference) |
| or a SUSPEND. |
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T1 | Earliest time at which the device may place | HS Reset T0 + 3. 0ms < T1 < HS Reset T0 |
| itself in FS mode after bus activity stops. | + 3.125ms |
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T2 | SIE samples LINESTATE. If LINESTATE = | T1 + 100µs < T2 < |
| SE0, then the SE0 on the bus is due to a | T1 + 875µs |
| Reset state. The device now enters the HS |
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| Detection Handshake protocol. |
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Revision 1.5 | 30 | SMSC USB3290 |
| DATASHEET |
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