USB3300_07 datasheet(36/55 Pages) SMSC

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Hi-Speed USB Host, Device or OTG PHY with ULPI Low Pin Interface

Datasheet

Revision 1.08 (11-07-07)

SMSC USB3300

DATASHEET

6.1.9.2

Exiting Low Power Mode

To exit Low Power Mode, the Link will assert STP. Upon the assertion of STP, the USB3300 will begin

its start-up procedure. After the PHY start-up is complete, the PHY will start the clock on CLKOUT and

de-assert DIR. Once DIR has been de-asserted, the Link can de-assert STP when ready and start

operating in Synchronous Mode. The PHY will automatically set the SuspendM bit to a 1 in the

Function Control register.

The time from T0 to T1 is given in Table 5.2, “Electrical Characteristics: CLKOUT Start-Up,” on

page 15.

Should the Link de-assert STP before DIR is de-asserted, the USB3300 will detect this as a false

resume request and return to Low Power Mode. This is detailed in section 3.9.4 of the ULPI 1.1

specification.

6.1.9.3

Interface Protection

ULPI protocol assumes that both the Link and PHY will keep the ULPI data bus driven by either the

Link when DIR is low or the PHY when DIR is high. The only exception is when DIR has changed

state and a turn around cycle occurs for 1 clock period.

In the design of a USB system, there can be cases where the Link may not be driving the ULPI bus

to a known state while DIR is low. Two examples where this can happen is because of a slow Link

start-up or a hardware reset.

START UP PROTECTION

Upon start-up, when the PHY de-asserts DIR, the Link must be ready to receive commands and drive

Idle on the data bus. If the Link is not ready to receive commands or drive Idle, it must assert STP

before DIR is de-asserted. The Link can then de-assert STP when it has completed its start-up. If the

Link doesn’t assert STP before it can receive commands, the PHY may interpret the databus state as

a TX CMD and transmit invalid data onto the USB bus, or make invalid register writes.

A Link should be designed to have the default POR state of the STP output high and the data bus tri-

stated. The USB3300 has weak pull-downs on the DATA bus to prevent these inputs from floating

when not driven.

Figure 6.9 Exiting Low Power Mode

DIR

CLK

DATA[7:0]

STP

NXT

TURN

AROUND

LOW

POWER MODE

DATA BUS IGNORED (SLOWLINK)

IDLE (FAST LINK)

IDLE

Slow Link Drives Bus

Idle and STP low

Fast Link Drives Bus

Idle and STP low

...

Note: Not to Scale

USB3300 Datasheet(PDF) 36 Page - SMSC Corporation

USB3300 Datasheet(HTML) 36 Page - SMSC Corporation

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