USB3450 datasheet(27/40 Pages) SMSC

27 / 40 page

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

Datasheet

SMSC USB3450

Revision 0.1 (05-11-05)

DATASHEET

Chapter 7 Application Notes

The following sections consist of select functional explanations to aid in implementing the USB3450

into a system. For complete description and specifications consult the Hi-Speed Transceiver Macrocell

Interface Specification and Universal Serial Bus Specification Revision 2.0.

7.1

Linestate

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 Hi-Speed 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 USB3450, 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 Link 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.

7.2

OPMODES

The OPMODE[1:0] pins allow control of the operating modes.

Table 7.1 Linestate States

STATE OF DP/DM LINES

LINESTATE[1:0]

FULL SPEED

XCVRSELECT =1

TERMSELECT=1

HIGH SPEED

XCVRSELECT =0

TERMSELECT=0

CHIRP MODE

XCVRSELECT =0

TERMSELECT=1

LS[1]

LS[0]

SE0

Squelch

HS Diff. Receiver Output

Invalid

Squelch

HS Diff. Receiver Output

SE1

Invalid

Table 7.2 Operational Modes

MODE[1:0]

STATE#

STATE NAME

DESCRIPTION

Normal Operation

Transceiver operates with normal USB data encoding and

decoding

Non-Driving

Allows the transceiver logic to support a soft disconnect feature

which tri-states both the HS and FS transmitters, and removes

any termination from the USB making it appear to an upstream

port that the device has been disconnected from the bus

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