BCM20705 Datasheet, PDF (34/67 Pages) Cypress Semiconductor – Single-Chip Bluetooth Transceiver and Baseband Processor

BCM20705 Data Sheet
UART Interface
UART Interface
The UART physical interface is a standard, 4-wire interface (RX, TX, RTS, CTS) with adjustable baud rates from
9600 bps to 4.0 Mbps. The interface features an automatic baud rate detection capability that returns a baud
rate selection. Alternatively, the baud rate can be selected via a vendor-specific UART HCI command. The
interface supports Bluetooth UART HCI (H4) specifications. The default baud rate for H4 is 115.2 Kbaud.
The following baud rates are supported:
• 9600
• 14400
• 19200
• 28800
• 38400
• 57600
• 115200
• 230400
• 460800
• 921600
• 144444
• 150000
• 2000000
• 3000000
• 3250000
• 3692000
• 4000000
Normally, the UART baud rate is set by a configuration record downloaded after reset or by automatic baud rate
detection. The host does not need to adjust the baud rate. Support for changing the baud rate during normal
HCI UART operation is provided through a vendor-specific command.
The BCM20705 UART operates with the host UART correctly, provided the combined baud rate error of the two
devices is within ±2%.
HCI 3-Wire Transport (UART H5)
The BCM20705 supports H5 UART transport for serial UART communications. H5 reduces the number of signal
lines required by eliminating CTS and RTS, when compared to H4.
H5 requires the use of an external LPO. CTS must be pulled low.
Broadcom®
Bluetooth Transceiver and Baseband Processor
November 13, 2014 • MCS20705-DS104-R
Page 33
BROADCOM CONFIDENTIAL