DS00002103A-page 29

USB3500

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 Link as possible, and the Link

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 USB3500 is reset from a suspend state, and the internal oscillator and clocks of the trans-

ceiver 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.

6.8

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 Link 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 6-3:

HS DETECTION HANDSHAKE TIMING BEHAVIOR (FS MODE)