USB3450 datasheet(37/40 Pages) SMSC

37 / 40 page

Hi-Speed USB Host or Device PHY With UTMI+ Interface

Datasheet

SMSC USB3450

Revision 0.1 (05-11-05)

DATASHEET

7.12

Detection of Resume

Resume signaling always takes place in FS mode (TERMSELECT and XCVRSELECT = FS enabled),

so the behavior for a HS device is identical to that of a FS device. The Link uses the LINESTATE

signals to determine when the USB transitions from the 'J' to the 'K' state and finally to the terminating

FS EOP (SE0 for 1.25us-1.5µs.).

The resume signaling (FS 'K') will be asserted for at least 20ms. At the beginning of this period the

Link may negate SUSPENDN, allowing the transceiver (and its oscillator) to power up and stabilize.

The FS EOP condition is relatively short. Links that simply look for an SE0 condition to exit suspend

mode do not necessarily give the transceiver’s clock generator enough time to stabilize. It is

recommended that all Link implementations key off the 'J' to 'K' transition for exiting suspend mode

(SUSPENDN = 1). And within 1.25µs after the transition to the SE0 state (low-speed EOP) the Link

must enable normal operation, i.e. enter HS or FS mode depending on the mode the device was in

when it was suspended.

Figure 7.7 Resume Timing Behavior (HS Mode)

Table 7.9 Resume Timing Values (HS Mode)

TIMING

PARAMETER

DESCRIPTION

VALUE

Internal device event initiating the resume

process

0 (reference)

Device asserts FS 'K' on the bus to signal

resume request to downstream port

T0 < T1 < T0 + 10ms.

The device releases FS 'K' on the bus. However

by this time the 'K' state is held by downstream

port.

T1 + 1.0ms < T2 < T1 + 15ms

Downstream port asserts SE0.

T1 + 20ms

Latest time at which a device, which was

previously in HS mode, must restore HS mode

after bus activity stops.

T3 + 1.33µs {2 Low-speed bit times}

USB3450 Datasheet(PDF) 37 Page - SMSC Corporation