USB3290 datasheet(22/46 Pages) SMSC

22 / 46 page

Small Footprint Hi-Speed USB 2.0 Device PHY with UTMI Interface

Datasheet

Revision 1.5 (11-02-07)

SMSC USB3290

DATASHEET

Figure 7.2 shows the relationship between CLKOUT and the receive data control signals in FS mode.

RXACTIVE "frames" a packet, transitioning only at the beginning and end of a packet. However

transitions of RXVALID may take place any time 8 bits of data are available. Figure 7.1 also shows

how RXVALID is only asserted for one CLKOUT cycle per byte time even though the data may be

presented for the full byte time. The XCVRSELECT signal determines whether the HS or FS timing

relationship is applied to the data and control signals.

7.3

Clock and Data Recovery Circuit

This block consists of the Clock and Data Recovery Circuit and the Elasticity Buffer. The Elasticity

Buffer is used to compensate for differences between the transmitting and receiving clock domains.

The USB 2.0 specification defines a maximum clock error of ±1000ppm of drift.

7.4

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 SIE 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 7.3.

Figure 7.2 FS CLK Relationship to Receive Data and Control Signals

Figure 7.3 Transmit Timing for a Data Packet

USB3290 Datasheet(PDF) 22 Page - SMSC Corporation