User's Manual

9/29/2004 OV4F2
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BCM2035 User Manual
04/23/03
Broadcom Corporation
Page 26 Transport Configuration Document 2035-UM100-R
TRANSPORT CONFIGURATION
The
BCM2035 supports the HCI UART and HCI USB transports, and either one may be selected in a particular
design. The transport selection is mutually exclusive, so it is not possible to use both USB and UART in a single
application. The selection of USB or UART as the HCI transport is sensed by the
BCM2035 Boot ROM after a
hardware reset has occurred. No special part number, HCI command, or configuration setting is needed to
select the transport.
To select UART as the transport, the
BCM2035 USB and UART signals should be connected as shown in
Figure 10. Connecting the USB signals to GND completely disables and powers off the USB transceiver,
eliminating excess current draw from the USB transceiver in UART designs. UP_RX must also be connected
to GND. The
BCM2035 will detect UART as the transport when UART_CTS_N is driven LOW by the Host.
Figure 10: BCM2035 UART Transport Configuration
Figure 11 shows the proper connection for using the BCM2035 with the USB transport. UART_CTS_N must
be strapped to VDD to prevent the BCM2035 from detecting activity on the CTS signal. The UART_RXD pin
should be connected to GND to prevent it from floating. The UP_RX signal must also be connected to GND.
The
BCM2035 will automatically detect activity on the USB transceiver when the device is connected to the
USB signals on the Host.
The USB_DETACH signal and the resistor network allow the
BCM2035 to control USB enumeration through
firmware. This is not necessary in all applications.
VDD_USB
USB_DP
USB_DN
UART_RXD
UART_TXD
UART_CTS_N
UART_RTS_N
USB_DETACH
RX
TX
CTS
RTS
HOST
Processor
BCM2035
UP_TX
UP_RX