USB2.0 PHY IC
Chapter 7 Functional Overview
Figure 2.1 Block Diagram on page 2 shows the functional block diagram of the GT3200, SMSC
USB3250. Each of the functions is described in detail below.
7.1
Modes of Operation
The GT3200, SMSC USB3250 support 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 transmit 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).
SMSC GT3200, SMSC USB3250
Revision 1.3 (10-05-04)
DATA1S8HEET
SMSC [ SMSC CORPORATION ]
