BCM88335 Data Sheet
UART Interface
The BCM88335 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 BCM88335 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
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 14: UART Timing
UART_CTS_N
UART_TXD
1
2
Midpoint of STOP bit
Midpoint of STOP bit
UART_RXD
3
UART_RTS_N
Broadcom®
September 23, 2015 • 88335-DS100-R
Page 49
BROADCOM CONFIDENTIAL
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