DS00002142A-page 19

USB3250

7.0

FUNCTIONAL OVERVIEW

FIGURE 2-1: Block Diagram on page 5 shows the functional block diagram of the USB3250. Each of the functions is

described in detail below.

7.1

Modes of Operation

The USB3250 supports two modes of operation. See Figure 7-1 for a block diagram of the digital interface.

• 8-bit unidirectional mode. Selected when DATABUS16_8 = 0. CLKOUT runs at 60MHz. The 8-bit transmit data

bus uses the lower 8 bits of the DATA bus (ie, TXDATA[7:0] = DATA[7:0]). The 8-bit receive data bus uses the

upper 8 bits of the DATA bus (ie, RXDATA[7:0] = DATA[15:8]).

• 16-bit bidirectional mode. Selected when DATABUS16_8 = 1. CLKOUT runs at 30MHz. An additional signal

(VALIDH) is used to identify whether the high byte of the respective 16-bit data word is valid. The full 16-bit DATA

bus is used for transmit and receive operations. If TXVALID is asserted, then the DATA[15:0] bus accepts trans-

mit data from the SIE. If TXVALID is deasserted, then the DATA[15:0] bus presents received data to the SIE.

VALIDH is undefined when DATABUS16_8 = 0 (8-bit mode).

FIGURE 7-1:

BIDIRECTIONAL 16-BIT INTERFACE

DATAOUT[7:0

]

TXVALI

D

DATA[7:0]

DATAOUT[1

5

:8]

DATA[15:8]

RXVALID

H

VALID

H

DATAIN[7:0]

DATAIN[15:8]

DATAOUT[7:0

]

MU

X

SELB

A

B

TXVALID

H

DATABUS16_

8

1=1

6

-bit mode, 0=8-bit mode

TXVALID

Transceiver

Core