USB3500 datasheet(43/46 Pages) SMSC

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

Datasheet

SMSC USB3500

Revision 1.0 (04-04-05)

DATASHEET

7.14

USB Reset and Chirp

The USB2.0 specification describes USB Reset as a means of attaching a FS or a HS Device to a

Host. This discussion will focus on a HS device connecting to a HS host.

Figure 7.9 shows the UTMI+ interface for both a Host (DPPD & DMPD = 1) and a Device (DPPD &

DMPD = 0). The following discussion applies to when the USB3500 is a configured as a Device and

is connected to another USB3500 configured as a Host. Since the Host and Device negotiate this

transition, both are discussed together and the user may follow this discussion for either a host or

device depending on the application of the USB3500. This sequence is also referred to as a “high-

speed chirp” due to the K-J pairs which the host sends to the downstream device.

Before the Host begins a session, it will set Xcvrselect to FS mode (10b) and Termselect to 1b to

activate the HS termination. The Host will also asserted the 15Kohm pull-down resistors on DP and

DM. The 15Kohm pull down resistors will pull DP and DM to 0 volts so that the Host Linestate will

return Single Ended Zero (SE0) when nothing is attached.

At time marker T0, the host link applies VBUS to the downstream port.

At T1, the Device has detected a valid voltage on VBUS and has asserted Termselect to enable the

1.5K ohm pull-up resistor on DP. During T1 the Host sees the linestate go from SEO to a J due to the

pull-up on DP.

Figure 7.9 USB Reset and Chirp

xcvrselect

termselect

opmode

txvalid

data

Device DPPD & DMPD == 0

HOST DPPD & DMPD == 1

vbus

xcvrselect

termselect

opmode

txvalid

linestate

data

5Volt

SE0

00h

Kseo

rxactive

rxvalid

K-J

Pairs

SE0

00-FF

SOF

A5h

Hs SOF packet

00h

USB3500 Datasheet(PDF) 43 Page - SMSC Corporation

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