sx1441 Semtech Corporation, sx1441 Datasheet - Page 53

• Manufacturer Part Number: sx1441
• Description: Bluetooth V1.2 Soc For Voice And Data Applications With Dsp Capabilities
• Manufacturer: Semtech Corporation

Personal Area Network
The ck32kHz low prescaler output can be selected as UART clock source if the bit Sel32k in RegUartFifoCtrl is
set. The baud rate selection follows Equation 4.
Ck32kHz can be generated from SLW_CLOCK_IN or the high prescaler input as described in 3.5.8.2. Table 93
shows the baud rate and the precision when SLW_CLOCK_IN is selected.
3.12.6 Transmission
The transmitter has to be enabled by setting UartEnTx. Data to be sent have to be written to the transmit FIFO
through the register RegUartFifoTx. The transmitter loads and sends data automatically, as long as the
transmission FIFO is not empty (bit UartTxFifoEmpty = 0) and the value on pad CTS is 0. When the transmit FIFO
is empty, the UartTxFifoEmpty bit returns to 1 and an interrupt is generated.
The bit UartTxFifoFull in RegUartFifoTxSta indicates that the transmit FIFO is full. If new data are written in the
FIFO while it is full, the bit UartTxFifoOerr is set to 1 and the last data are ignored. The bit UartTxFifoOerr is
cleared when the register RegUartFifoTxSta is read.
The bit UartTxBusy in RegUartFifoTxSta shows that the transmitter is busy transmitting a word.
Writing in RegUartFifoTxSta resets the transmitter block. Data in the FIFO that were not transmitted are lost. The
flags in RegUartFifoTxSta are reset.
Figure 24 and
Figure 25 show an UART transmission. The figures are drawn with a FIFO depth of 2, for simplification, although
the FIFO depth is 8.
© Semtech 2006
UartRcDiv
0000
0001
0011
0111
UartRcDiv
Table 93 - Baud rate selection (Sel32k = 1, EnableSwClock = 1)
Baud rate (Bd/s)
2400
1200
600
300
01111
10000
10001
10010
10011
10100
10101
10110
10111
11000
11001
11010
11011
11100
11101
11110
11111
Baudrate
Table 92 - Division factor for UartRcDiv
Equation 4 – Baudrate vs. ck32kHz
=
14
⋅
SLW_CLOCK_IN frequency
32’000 Hz
- 4.8 %
- 4.8 %
- 4.8 %
- 5 %
53
factorUart
factorUartRcDiv
f
ck
32
kHz
RcDiv
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
SX1441 – Bluetooth® 1.2 SoC
32’768 Hz
- 2.5 %
- 2.5 %
- 2.5 %
- 2.5 %
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Data Sheet