ADVANCE
CYW43570
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 CYW43570 UARTs
operate correctly with the host UART as long as the combined baud rate error of the two devices is within ±2%.
Table 14. Example of Common Baud Rates
Desired Rate
Actual Rate
Error (%)
4000000
3692000
3000000
2000000
1500000
1444444
921600
460800
230400
115200
57600
4000000
3692308
3000000
2000000
1500000
1454544
923077
461538
230796
115385
57692
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
38400
38400
28800
28846
19200
19200
14400
14423
9600
9600
Figure 16. UART Timing
BT_UART_CTS_L
1
2
BT_UART_TXD
Midpoint of STOP bit
Midpoint of STOP bit
BT_UART_RXD
3
BT_UART_RTS_L
Table 15. UART Timing Specifications
Reference Characteristics
Minimum
Typical
Maximum
1.5
Unit
1
2
Delay time, BT_UART_CTS_L low to BT_UART_TXD valid
–
–
–
Bit periods
Bit periods
Setup time, BT_UART_CTS_L high before midpoint of stop
bit
–
0.5
3
Delay time, midpoint of stop bit to BT_UART_RTS_L high
–
–
0.5
Bit periods
Document Number: 002-15054 Rev. *I
Page 33 of 94
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