USB3450

DS00002105A-page 28

6.10

HS Detection Handshake – Suspend Timing

If reset is entered from a suspended state, the internal oscillator and clocks of the transceiver are assumed to be pow-

ered down. Figure 6-6 shows how CLKOUT is used to control the duration of the chirp generated by the device.

When reset is entered from a suspended state (J to SE0 transition reported by LINESTATE), SUSPENDN is combina-

torially negated at time T0 by the Link. It takes approximately 5 milliseconds for the transceiver's oscillator to stabilize.

The device does not generate any transitions of the CLKOUT signal until it is “usable” (where “usable” is defined as

stable to within ±10% of the nominal frequency and the duty cycle accuracy 50±5%).

The first transition of CLKOUT occurs at T1. The Link then sets OPMODE to Disable Bit Stuffing and NRZI encoding,

XCVRSELECT to HS mode, and must assert a Chirp K for 66000 CLKOUT cycles to ensure a 1ms minimum duration.

If CLKOUT is 10% fast (66MHz) then Chirp K will be 1.0ms. If CLKOUT is 10% slow (54 MHz) then Chirp K will be 1.2ms.

The 5.6ms requirement for the first CLKOUT transition after SUSPENDN, ensures enough time to assert a 1ms Chirp

K and still complete before T3. Once the Chirp K is completed (T3) the Link can begin looking for host chirps and use

CLKOUT to time the process. At this time, the device follows the same protocol as in Section 6.9, "HS Detection Hand-

shake – HS Downstream Facing Port" for completion of the High Speed Handshake.

LINESTATE signals asserted continuously for 165 CLKOUT cycles.

FIGURE 6-6:

HS DETECTION HANDSHAKE TIMING BEHAVIOR FROM SUSPEND

CLK60

Look for host chirps

Device Chirp K

SUSPENDN

DP/DM

TERMSELECT

TXVALID

SE0

J

CLK power up time

XCVRSELECT

OPMODE 1

OPMODE 0

time

T0

T3

T4

T1

T2