gt3200 SMC Corporation, gt3200 Datasheet - Page 34

• Manufacturer Part Number: gt3200
• Description: Usb2.0 Phy Ic
• Manufacturer: SMC Corporation

Revision 1.3 (10-05-04)
8.5
8.6
PARAMETER
HS Reset T0
TIMING
TERMSELECT
XCVRSELECT
T1
T2
For HS operation, IDLE is a SE0 state on the bus. SE0 is also used to reset a HS device. A HS
device cannot use the 2.5us assertion of SE0 (as defined for FS operation) to indicate reset since the
bus is often in this state between packets. If no bus activity (IDLE) is detected for more than 3ms, a
HS device must determine whether the downstream facing port is signaling a suspend or a reset. The
following section details how this determination is made. If a reset is signaled, the HS device will then
initiate the HS Detection Handshake protocol.
If a device in HS mode detects bus inactivity 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
SIE must then check LINESTATE for the SE0 condition. If SE0 is asserted at time T2, then the
upstream port is forcing the reset state to the device (i.e., a Driven SE0). The device will then initiate
the HS detection handshake protocol.
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
Reset Detection
Suspend Detection
DP/DM
time
Bus activity ceases, signaling either a reset or a
SUSPEND.
Earliest time at which the device may place itself in
FS mode after bus activity stops.
SIE samples LINESTATE. If LINESTATE = SE0, then
the SE0 on the bus is due to a Reset state. The
device now enters the HS Detection Handshake
protocol.
Activity
x x x x x x
x x x x x x
x x x x x x
Last
T0
Figure 8.1 Reset Timing Behavior (HS Mode)
Table 8.4 Reset Timing Values (HS Mode)
DESCRIPTION
DATASHEET
Driven SE0
29
T1
0 (reference)
HS Reset T0 + 3. 0ms < T1 < HS
Reset T0 + 3.125ms
T1 + 100µs < T2 < T1 + 875µs
SMSC GT3200, SMSC USB3250
T2
HS Detection
Handshake
VALUE
USB2.0 PHY IC