Datasheet

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

Datasheet

Revision 1.1 (01-24-13) 32 SMSC USB3300

DATASHEET

6.1.5.2 ULPI Register Read

A ULPI register read operation is given in Figure 6.5. The Link drives a TXD CMD byte with DATA[7:6]

= 11h for a register read. DATA[5:0] of the ULPI TXD command bye contain the register address.

At T0, the Link will place the TXD CMD on the databus. At T2, the PHY will bring NXT high, signaling

that the Link it is ready to accept the data transfer. At T3, the PHY reads the TXD CMD, determines

it is a register read, and asserts DIR to gain control of the bus. The PHY will also de-assert NXT. At

T4, the bus ownership has transferred back to the PHY and the PHY drives the requested register

onto the databus. At T5, the Link will read the databus and the PHY will drop DIR low returning control

of the bus back to the Link. After the turn around cycle, the Link must drive a ULPI Idle command at T6.

6.1.6 ULPI RXD CMD

The Link needs several more important states of information which were provided by the linestate[1:0],

rxactive, rxvalid and rxerror. When an implementing the OTG functions the Vbus and ID pin states

must also be transferred into the Link.

ULPI defines a Receive Command Byte (RXD CMD) that contains this information. The Encoding of

the RXD CMD byte is given in the Table 6.5, "ULPI RX CMD Encoding".

Transfer of the RXD CMD byte occurs when in Synchronous Mode when the PHY has control of the

bus. Transfers of the RXD CMD occur after: a transmit cmd has issued STP, a linestate change when

not transmitting, a USB receive, or an interrupt event occurs.

In Figure 6.2, "ULPI Digital Block Diagram", the ULPI Protocol Block determines when to send an RXD

CMD. When a linestate change occurs the RXD CMD is sent immediately if the DIR output is low.

When a USB Receive is occurring RXD CMDs are sent when ever NXT = 0 and DIR = 1. When a

USB Transmit occurs the RXD CMDs are returned to the Link after the STP is asserted ending the

Link to USB3300 transfer of the bytes to be sent on the transmit.

To summarize a RXD CMD transfer occurs:

 when DIR is low and a linestate change occurs.

 when Vbus and/or ID comparators change state.

Figure 6.5 ULPI Register Read

DIR

CLK

DATA[7:0]

STP

NXT

Txd Cmd Reg

Read

Idle

Reg DataTurn around Turn around

T1 T2 T3 T4 T5 T6

Idle