USB3320 datasheet(36/70 Pages) MICROCHIP

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USB3320

DS00001792B-page 36

 2014-2015 Microchip Technology Inc.

6.2.1

ULPI REGISTER WRITE

A ULPI register write operation is given in Figure 6-3. The TXD command with a register write DATA[7:6] = 10b is driven

by the Link at T0. The register address is encoded into DATA[5:0] of the TXD CMD byte.

To write a register, the Link will wait until DIR is low, and at T0, drive the TXD CMD on the data bus. At T2 the transceiver

will drive NXT high. On the next rising clock edge, T3, the Link will write the register data. At T4, the transceiver will

accept the register data and drive NXT low. The Link will drive an Idle on the bus and drive STP high to signal the end

of the data packet. Finally, at T5, the transceiver will latch the data into the register and the Link will pull STP low.

NXT

is used to control when the Link drives the register data on the bus. DIR is low throughout this transaction since

the transceiver is receiving data from the Link. STP is used to end the transaction and data is registered after the de-

assertion of STP. After the write operation completes, the Link must drive a ULPI Idle (00h) on the data bus or the

USB3320 may decode the bus value as a ULPI command.

A ULPI extended register write operation is shown in Figure 6-4. To write an extended register, the Link will wait until

DIR

is low, and at T0, drive the TXD CMD on the data bus. At T2 the transceiver will drive NXT high. On the next clock

T3 the Link will drive the extended address. On the next rising clock edge, T4, the Link will write the register data. At

T5, the transceiver will accept the register data and drive NXT low. The Link will drive an Idle on the bus and drive STP

high to signal the end of the data packet. Finally, at T5, the transceiver will latch the data into the register. The Link will

pull STP low.

FIGURE 6-3:

ULPI REGISTER WRITE IN SYNCHRONOUS MODE

DIR

CLK

DATA[7:0]

STP

NXT

TXD CMD

(reg write)

Idle

Reg Data[n]

Idle

ULPI Register

Reg Data [n-1]

Reg Data [n]

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