Uart Interface - Infineon Cypress CYW43353 Manual

7.2 UART Interface

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 inter-
face 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 CYW43353 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 CYW43353
UARTs operate correctly with the host UART as long as the combined baud rate error of the two devices is within ±2%.
Table 9. Example of Common Baud Rates
Desired Rate
4000000
3692000
3000000
2000000
1500000
1444444
921600
460800
230400
115200
57600
38400
28800
19200
14400
9600
Document Number: 002-14949 Rev. *G
PRELIMINARY
Actual Rate
4000000
3692308
3000000
2000000
1500000
1454544
923077
461538
230796
115385
57692
38400
28846
19200
14423
9600
CYW43353
Error (%)
0.00
0.01
0.00
0.00
0.00
0.70
0.16
0.16
0.17
0.16
0.16
0.00
0.16
0.00
0.16
0.00
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