USB334X datasheet(52/92 Pages) MICROCHIP

52 / 92 page

USB334x

DS00002646A-page 52

 2009-2018 Microchip Technology Inc.

6.3.2

USB RECEIVER

The USB334x ULPI receiver fully supports HS, FS, and LS transmit operations. In all three modes the receiver detects

the start of packet and synchronizes to the incoming data packet. In the ULPI protocol, a received packet has the priority

and will immediately follow register reads and RXCMD transfers. Figure 6-8 shows a basic USB packet received by the

USB334x over the ULPI interface.

In Figure 6-8 the PHY asserts DIR to take control of the data bus from the Link. The assertion of DIR and NXT in the

same cycle contains additional information that Rxactive has been asserted. When NXT is de-asserted and DIR is

asserted, the RXCMD data is transferred to the Link. After the last byte of the USB receive packet is transferred to the

PHY, the linestate will return to idle.

The ULPI Full Speed receiver operates according to the UTMI / ULPI specification. In the Full Speed case, the NXT

signal will assert only when the Data bus has a valid received data byte. When NXT is low with DIR high, the RXCMD

is driven on the data bus.

In Full Speed, the USB334x will not issue a Rxactive de-assertion in the RXCMD until the DP/DM linestate transitions

to idle. This prevents the Link from violating the two Full Speed bit times minimum turn around time.

6.3.2.1

Disconnect Detection

A Hi-Speed host must detect a disconnect by sampling the transmitter outputs during the long EOP transmitted during

a SOF packet. The USB334x only looks for a Hi-Speed disconnect during the long EOP where the period is long enough

for the disconnect reflection to return to the host PHY. When a Hi-Speed disconnect occurs, the USB334x will return a

RXCMD and set the host disconnect bit in the USB Interrupt Status register.

When in FS or LS modes, the Link is expected to handle all disconnect detection.

6.3.2.2

Link Power Management (LPM) Token Receive

The USB334x is fully capable of receiving the Extended PID in the LPM token. When the LPM 0000b PID is received,

this information is passed to the Link as a normal receive packet. If the Link chooses to enter LPM suspend, the proce-

dure detailed in Section 6.5.3, "Link Power Management (LPM)," on page 57 can be followed.

6.4

USB334x Transmitter

The USB334x ULPI transmitter fully supports HS, FS, and LS transmit operations. Figure 6-1 shows the Hi-Speed, Full

Speed, and Low Speed transmitter block controlled by ULPI Protocol Block. Encoding of the USB packet follows the bit-

stuffing and NRZI outlined in the USB 2.0 specification. Many of these functions are reused between the HS and FS/LS

transmitters. When using the USB334x, Table 5-1 should always be used as a guideline on how to configure for various

FIGURE 6-8:

ULPI RECEIVE IN SYNCHRONOUS MODE

DIR

CLK

DATA[7:0]

STP

NXT

Rxd

Cmd

Idle

Turn

around

PID

Rxd

Cmd

Turn

around

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