USB3500

DS00002103A-page 28

6.6

Suspend Detection

If a HS device detects SE0 asserted on the bus for more than 3ms (T1), it reverts to FS mode. This enables the FS pull-

up on the DP line in an attempt to assert a continuous FS J state on the bus. The Link must then check LINESTATE for

the J condition. If J is asserted at time T2, then the upstream port is asserting a soft SE0 and the USB is in a J state

indicating a suspend condition. By time T4 the device must be fully suspended.

6.7

HS Detection Handshake

The downstream facing port asserting an SE0 state on the bus initiates the HS Detection Handshake.

There are three ways in which a device may enter the HS Handshake Detection process:

1.

If the device is suspended and it detects an SE0 state on the bus it may immediately enter the HS handshake

detection process.

2.

If the device is in FS mode and an SE0 state is detected for more than 2.5µs. it may enter the HS handshake

detection process.

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 Link must check the LINESTATE signals. If a J state is

FIGURE 6-2:

SUSPEND TIMING BEHAVIOR (HS MODE)

TABLE 6-6:

SUSPEND TIMING VALUES (HS MODE)

Timing Parameter

Description

Value

HS Reset T0

End of last bus activity, signaling either a reset

or a SUSPEND.

0 (reference)

T1

The time at which the device must place itself in

FS mode after bus activity stops.

HS Reset T0 + 3. 0ms < T1 < HS Reset T0

+ 3.125ms

T2

Link samples LINESTATE. If LINESTATE = 'J',

then the initial SE0 on the bus (T0 - T1) had

been due to a Suspend state and the Link

remains in HS mode.

T1 + 100 µs < T2 <

T1 + 875µs

T3

The earliest time where a device can issue

Resume signaling.

HS Reset T0 + 5ms

T4

The latest time that a device must actually be

suspended, drawing no more than the suspend

current from the bus.

HS Reset T0 + 10ms