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

Datasheet

SMSC USB3450

21

Revision 0.1 (05-11-05)

DATASHEET

6.2

TX Logic

This block receives parallel data bytes placed on the DATA bus and performs the necessary transmit

operations. These operations include parallel to serial conversion, bit stuffing and NRZI encoding.

Upon valid assertion of the proper TX control lines by the Link and TX State Machine, the TX LOGIC

block will synchronously shift, at either the FS or HS rate, the data to the FS/HS TX block to be

transmitted on the USB cable. Data transmit timing is shown in Figure 6.3.

The behavior of the Transmit State Machine is described below.

■

The Link asserts TXVALID to begin a transmission.

■

After the Link asserts TXVALID it can assume that the transmission has started when it detects

TXREADY has been asserted.

■

The Link must assume that the USB3450 has consumed a data byte if TXREADY and TXVALID

are asserted on the rising edge of CLKOUT.

■

The Link must have valid packet information (PID) asserted on the DATA bus coincident with the

assertion of TXVALID.

■

TXREADY is sampled by the Link on the rising edge of CLKOUT.

■

The Link negates TXVALID to complete a packet. Once negated, the transmit logic will never

reassert TXREADY until after the EOP has been generated. (TXREADY will not re-assert until

TXVALD asserts again.

■

The USB3450 is ready to transmit another packet immediately, however the Link must conform to

the minimum inter-packet delays identified in the Hi-Speed specification.

■

Supports high speed disconnect detect through the HOSTDISC pin. In Host mode the USB3450

will sample the disconnect comparator at the 32nd bit of the 40 bit long EOP during SOF packets.

■

Supports FS pre-amble for FS hubs with a LS device.

■

Supports LS keep alive by receiving the SOF PID.

■

Supports Host mode resume K which ends with two low speed times of SE0 followed by 1 FS “J”.

6.3

RX Logic

This block receives serial data from the clock recovery circuits and processes it to be transferred to

the Link on the DATA bus. The processing involved includes NRZI decoding, bit unstuffing, and serial

to parallel conversion. Upon valid assertion of the proper RX control lines, the RX Logic block will

provide bytes to the DATA bus as shown in the figures below. The behavior of the receiver is described

below.

Figure 6.3 Transmit Timing for a Data Packet