USB3450 datasheet(38/40 Pages) SMSC

38 / 40 page

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

Datasheet

Revision 0.1 (05-11-05)

SMSC USB3450

DATASHEET

If the device was in FS mode: then the Link leaves the FS terminations enabled. After the SE0 expires,

the downstream port will assert a J state for one low-speed bit time, and the bus will enter a FS Idle

state (maintained by the FS terminations).

If the device was in HS mode: then the Link must switch to the FS terminations before the SE0 expires

(< 1.25µs). After the SE0 expires, the bus will then enter a HS IDLE state (maintained by the HS

terminations).

7.13

HS Device Attach

Figure 7.8 demonstrates the timing of the USB3450 control signals during a device attach event. When

a HS device is attached to an upstream port, power is asserted to the device and the device sets

XCVRSELECT and TERMSELECT to FS mode (time T1).

VBUS is the +5V power available on the USB cable. Device Reset in Figure 7.8 indicates that VBUS is

within normal operational range as defined in the Hi-Speed specification. The assertion of Device

Reset (T0) by the upstream port will initialize the device. By monitoring LINESTATE, the Link state

machine knows to set the XCVRSELECT and TERMSELECT signals to FS mode (T1).

The standard FS technique of using a pull-up resistor on DP to signal the attach of a FS device is

employed. The Link must then check the LINESTATE signals for SE0. If LINESTATE = SE0 is asserted

at time T2 then the upstream port is forcing the reset state to the device (i.e. Driven SE0). The device

will then reset itself before initiating the HS Detection Handshake protocol.

Figure 7.8 Device Attach Behavior

Table 7.10 Attach and Reset Timing Values

TIMING

PARAMETER

DESCRIPTION

VALUE

Vbus Valid.

0 (reference)

Maximum time from Vbus valid to when the device

must signal attach.

T0 + 100ms < T1

(HS Reset T0)

Debounce interval. The device now enters the HS

Detection Handshake protocol.

T1 + 100ms < T2

USB3450 Datasheet(PDF) 38 Page - SMSC Corporation