
USB2.0 PHY IC
SMSC GT3200, SMSC USB3250
30
Revision 1.3 (10-05-04)
DATASHEET
SIE 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.
8.7
HS Detection Handshake
The High Speed Detection Handshake process is entered from one of three states: suspend, active
FS or active HS. The downstream facing port asserting an SE0 state on the bus initiates the HS
Detection Handshake. Depending on the initial state, an SE0 condition can be asserted from 0 to 4
ms before initiating the HS Detection Handshake. These states are described in the USB2.0
specification.
There are three ways in which a device may enter the HS Handshake Detection process:
Figure 8.2 Suspend Timing Behavior (HS Mode)
Table 8.5 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
SIE samples LINESTATE. If LINESTATE = 'J', then
the initial SE0 on the bus (T0 - T1) had been due
to a Suspend state and the SIE 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
Last
Activity
'J' State
Soft SE0
Device is suspended
SUSPENDN
XCVRSELECT
DP/DM
TERMSELECT
time
T2
T0
T1
T3
T4