USB3250 Standard Microsystems Corporation, USB3250 Datasheet - Page 32

• Manufacturer Part Number: USB3250
• Description: Usb2.0 PHY IC
• Manufacturer: Standard Microsystems Corporation

Chapter 8 Application Notes
Revision 1.5 (03-24-06)
8.1
LS[1]
0
0
1
1
LINESTATE[1:0]
The following sections consist of select functional explanations to aid in implementing the PHY into a
system. For complete description and specifications consult the USB2.0 Transceiver Macrocell
Interface Specification and Universal Serial Bus Specification Revision 2.0.
The voltage thresholds that the LINESTATE[1:0] signals use to reflect the state of DP and DM depend
on the state of XCVRSELECT. LINESTATE[1:0] uses HS thresholds when the HS transceiver is
enabled (XCVRSELECT = 0) and FS thresholds when the FS transceiver is enabled (XCVRSELECT
= 1). There is not a concept of variable single-ended thresholds in the USB2.0 specification for HS
mode.
The HS receiver is used to detect Chirp J or K, where the output of the HS receiver is always qualified
with the Squelch signal. If squelched, the output of the HS receiver is ignored. In the PartNumber, as
an alternative to using variable thresholds for the single-ended receivers, the following approach is
used.
In HS mode, 3ms of no USB activity (IDLE state) signals a reset. The SIE monitors LINESTATE[1:0]
for the IDLE state. To minimize transitions on LINESTATE[1:0] while in HS mode, the presence of
!Squelch is used to force LINESTATE[1:0] to a J state.
Linestate
LS[0]
0
1
0
1
Table 8.1 Linestate States
XCVRSELECT =1
TERMSELECT=1
FULL SPEED
DATASHEET
SE0
SE1
K
J
STATE OF DP/DM LINES
32
XCVRSELECT =0
TERMSELECT=0
HIGH SPEED
!Squelch
Squelch
Invalid
Invalid
SMSC GT3200, SMSC USB3250
Differential Receiver
Differential Receiver
XCVRSELECT =0
TERMSELECT=1
!Squelch & !HS
!Squelch & HS
CHIRP MODE
Squelch
Output
Output
Invalid
USB2.0 PHY IC
Datasheet