Datasheet

Highly Integrated Full Featured Hi-Speed USB 2.0 ULPI Transceiver
Datasheet
Revision 1.0 (07-14-09) 58 SMSC USB3320
DATASHEET
6.5.1 USB UART Mode
The USB3320 can be placed into UART Mode by first setting the TxdEn and RxdEn bits in the Carkit
Control register. Then the Link can set the CarkitMode bit in the Interface Control register. The TxdEn
and RxdEn bits must be written before the CarkitMode bit.
After the CarkitMode bit is set, the ULPI interface will become redefined as described in Ta b le 6. 8 , and
the USB3320 will transmit data through the DATA[0] to DM of the USB connector and receive data on
DP and pass the information the Link on DATA[1].
When entering UART mode, the regulator output will automatically switch to the value configured by
the UART RegOutput bits in the USB IO & Power Management register and a pull-up will be applied
internally to DP and DM. This will hold the UART in its default operating state.
While in UART mode, the transmit edge rates can be set to either the Full Speed USB or Low Speed
USB edge rates by using the XcvrSelect[1:0] bits in the Function Control register.
Table 6.7 ULPI Register Programming Example to Enter UART Mode
R/W
ADDRESS
(HEX)
VALUE
(HEX) DESCRIPTION RESULT
W 04 49 Configure Non-Driving mode
Select FS transmit edge rates
OpMode=01
XcvrSelect=01
W 39 00 Set regulator to 3.3V UART RegOutput=00
W 19 0C Enable UART connections RxdEn=1
TxdEn=1
W 07 04 Enable carkit mode CarkitMode=1
Table 6.8 Pin Definitions in Carkit Mode
SIGNAL
CONNECTED
TO DIRECTION DESCRIPTION
txd DATA[0] IN UART TXD signal that is routed to the DM pin if the TxdEn
is set in the Carkit Control register.
rxd DATA[1] OUT UART RXD signal that is routed to the DP pin if the RxdEn
bit is set in the Carkit Control register.
reserved DATA[2]
OUT Driven Low.
int DATA[3] OUT Asserted when any unmasked interrupt occurs. Active high.
reserved DATA[4:7] OUT Driven Low.