BCM4354 datasheet(39/165 Pages) CYPRESS

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Document Number: 002-14809 Rev. *J

Page 39 of 165

CYW4354

7.5 UART Interface

The CYW4354 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 4.1 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 CYW4354 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 CYW4354 UARTs

operate correctly with the host UART as long as the combined baud rate error of the two devices is within ±2%.

Table 15. Example of Common Baud Rates

Desired Rate

Actual Rate

Error (%)

4000000

0.00

3692000

3692308

0.01

3000000

0.00

2000000

0.00

1500000

0.00

1444444

1454544

0.70

921600

923077

0.16

460800

461538

0.16

230400

230796

0.17

115200

115385

0.16

57600

57692

0.16

38400

0.00

28800

28846

0.16

19200

0.00

14400

14423

0.16

9600

0.00

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