DS00002142A-page 31

USB3250

3.

If the device is in HS mode and an SE0 state is detected for more than 3.0ms. it may enter the HS handshake

detection process. In HS mode, a device must first determine whether the SE0 state is signaling a suspend or a

reset condition. To do this the device reverts to FS mode by placing XCVRSELECT and TERMSELECT into FS

mode. The device must not wait more than 3.125ms before the reversion to FS mode. After reverting to FS mode,

no less than 100µs and no more than 875µs later the SIE must check the LINESTATE signals. If a J state is

detected the device will enter a suspend state. If an SE0 state is detected, then the device will enter the HS Hand-

shake detection process.

In each case, the assertion of the SE0 state on the bus initiates the reset. The minimum reset interval is 10ms. Depend-

ing on the previous mode that the bus was in, the delay between the initial assertion of the SE0 state and entering the

HS Handshake detection can be from 0 to 4ms.

This transceiver design pushes as much of the responsibility for timing events on to the SIE as possible, and the SIE

requires a stable CLKOUT signal to perform accurate timing. In case 2 and 3 above, CLKOUT has been running and is

stable, however in case 1 the PHY is reset from a suspend state, and the internal oscillator and clocks of the transceiver

are assumed to be powered down. A device has up to 6ms after the release of SUSPENDN to assert a minimum of a

1ms Chirp K.

8.8

HS Detection Handshake - FS 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 host port.

If the downstream facing port is not HS capable, then the HS K asserted by the device is ignored and the alternating

sequence of HS Chirp K's and J's is not generated. If no chirps are detected (T4) by the device, it will enter FS mode

by returning XCVRSELECT to FS mode.

FIGURE 8-3:

HS DETECTION HANDSHAKE TIMING BEHAVIOR (FS MODE)

No

Downstream

Facing Port

Chirps

SE0

SOF

FS Mode

Device Chirp K

TXVALID

TERMSELECT

DP/DM

XCVRSELECT

OPMODE 1

OPMODE 0

time

T1

T2

T0

T4

T5

T3