USB3250 datasheet(38/48 Pages) SMSC

38 / 48 page

USB2.0 PHY IC

Datasheet

Revision 1.5 (03-24-06)

SMSC GT3200, SMSC USB3250

DATASHEET

8.9

HS Detection Handshake - HS Downstream Facing Port

Upon entering the HS Detection process (T0) XCVRSELECT and TERMSELECT are in FS mode. The

DP pull-up is asserted and the HS terminations are disabled. The SIE then sets OPMODE to Disable

Bit Stuffing and NRZI encoding, XCVRSELECT to HS mode, and begins the transmission of all 0's

data, which asserts a HS K (chirp) on the bus (T1). The device chirp must last at least 1.0ms, and

must end no later than 7.0ms after HS Reset T0. At time T1 the device begins listening for a chirp

sequence from the downstream facing port. If the downstream facing port is HS capable then it will

begin generating an alternating sequence of Chirp K's and Chirp J's (T3) after the termination of the

chirp from the device (T2). After the device sees the valid chirp sequence Chirp K-J-K-J-K-J (T6), it

will enter HS mode by setting TERMSELECT to HS mode (T7).

Figure 8.4 provides a state diagram for Chirp K-J-K-J-K-J validation. Prior to the end of reset (T9) the

device port must terminate the sequence of Chirp K's and Chirp J's (T8) and assert SE0 (T8-T9). Note

that the sequence of Chirp K's and Chirp J's constitutes bus activity.

The Chirp K-J-K-J-K-J sequence occurs too slow to propagate through the serial data path, therefore

LINESTATE signal transitions must be used by the SIE to step through the Chirp K-J-K-J-K-J state

diagram, where "K State" is equivalent to LINESTATE = K State and "J State" is equivalent to

LINESTATE = J State. The SIE must employ a counter (Chirp Count) to count the number of Chirp K

and Chirp J states. Note that LINESTATE does not filter the bus signals so the requirement that a bus

state must be "continuously asserted for 2.5µs" must be verified by the SIE sampling the LINESTATE

signals.

Figure 8.4 Chirp K-J-K-J-K-J Sequence Detection State Diagram

Detect K?

Start Chirp

K-J-K-J-

K-J

detection

INC

Chirp

Count

K State

State

Detect J?

INC

Chirp

J State

Chirp Count != 6

& !SE0

Chirp

Count = 0

Chirp Count

!= 6

& !SE0

Chirp

Valid

Chirp

Invalid

SE0

Chirp Count

=6 6 66

USB3250 датащи(PDF) 38 Page - SMSC Corporation

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