Hi-Speed USB Device PHY with UTMI Interface

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 pull-up on the DP line in an attempt to assert a continuous FS J state on the bus. The SIE must then check LINESTATE for the SE0 condition. If SE0 is asserted at time T2, then the upstream port is forcing the reset state to the device (i.e., a Driven SE0). The device will then initiate the HS detection handshake protocol.

Figure 8.1 Reset Timing Behavior (HS Mode)

Table 8.4 Reset Timing Values (HS Mode)

TIMING

 

 

PARAMETER

DESCRIPTION

VALUE

 

 

 

HS Reset T0

Bus activity ceases, signaling either a reset

0 (reference)

 

or a SUSPEND.

 

 

 

 

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

 

 

 

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

 

 

Detection Handshake protocol.

 

 

 

 

Revision 1.5 (11-15-07)

30

SMSC USB3280

 

DATASHEET