USB3250 Standard Microsystems Corporation, USB3250 Datasheet - Page 38

• Manufacturer Part Number: USB3250
• Description: Usb2.0 PHY IC
• Manufacturer: Standard Microsystems Corporation

Revision 1.5 (03-24-06)
8.9
Start Chirp
detection
K-J-K-J-
K-J
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
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.
HS Detection Handshake - HS Downstream Facing Port
Count = 0
Chirp
Figure 8.4 Chirp K-J-K-J-K-J Sequence Detection State Diagram
provides a state diagram for Chirp K-J-K-J-K-J validation. Prior to the end of reset (T9) the
Detect K?
Detect J?
Chirp Count != 6
State
DATASHEET
!K
!J
& !SE0
Chirp Count
38
& !SE0
K State
!= 6
J State
Chirp
Count
Chirp
INC
INC
SMSC GT3200, SMSC USB3250
SE0
Chirp Count
=6 6 66
Chirp
Invalid
Chirp
Valid
USB2.0 PHY IC
Datasheet