BCM4339 Preliminary Data Sheet
UART Interface
Table 12: USB Full-Speed Timing Specifications
Reference Characteristics
Minimum
Maximum
Unit
1
2
3
4
Transition rise time
Transition fall time
4
20
ns
4
20
ns
Rise/fall timing matching
Full-speed data rate
90
111
%
12 – 0.25%
12 + 0.25%
Mb/s
Figure 17: USB Full-Speed Timing
2
1
D+
D-
90%
90%
VCRS
10%
10%
UART Interface
The BCM4339 shares a single UART for Bluetooth and FM. The UART is a standard 4-wire interface (RX, TX,
RTS, and 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 may be selected through
a vendor-specific UART HCI command.
UART has a 1040-byte receive FIFO and a 1040-byte transmit FIFO to support EDR. Access to the FIFOs is
conducted through the AHB interface through either DMA or the CPU. The UART supports the Bluetooth 4.1
UART HCI specification: H4, a custom Extended H4, and H5. The default baud rate is 115.2 Kbaud.
The UART supports the 3-wire H5 UART transport, as described in the Bluetooth specification (“Three-wire
UART Transport Layer”). Compared to H4, the H5 UART transport reduces the number of signal lines required
by eliminating the CTS and RTS signals.
The BCM4339 UART can perform XON/XOFF flow control and includes hardware support for the Serial Line
Input Protocol (SLIP). It can also perform wake-on activity. For example, activity on the RX or CTS inputs can
wake the chip from a sleep state.
Normally, the UART baud rate is set by a configuration record downloaded after device reset, or by automatic
baud rate detection, and the host does not need to adjust the baud rate. Support for changing the baud rate
during normal HCI UART operation is included through a vendor-specific command that allows the host to adjust
the contents of the baud rate registers. The BCM4339 UARTs operate correctly with the host UART as long as
the combined baud rate error of the two devices is within ±2%.
Broadcom®
November 17, 2014 • 4339-DS106-R
Page 59
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