XE8806A SEMTECH [Semtech Corporation], XE8806A Datasheet - Page 93

• Manufacturer Part Number: XE8806A
• Description: Ultra Low-Power Low-Voltage
• Manufacturer: SEMTECH [Semtech Corporation]

14.10 Baud rate selection
In order to have correct baud rates, the interface has to be fed with a stable and trimmed clock source. The clock
source can be an external clock source or the RC oscillator. The precision of the baud rate will depend on the
precision of the selected clock source. The choice between the RC oscillator and the external clock source is made
with the bit EnExtClock in RegSysClock. The precision of the obtained baud rate is directly proportional to the
frequency deviation of the used clock source.
The bits RfifBRCoarse[1:0] and RfifBRFine[3:0] in RegRfifCmd1 are used to select the appropriate baud rate.
Several RC division factors are available.
The expression of the baud rate is the following:
with:
Note that the baud rate is the rate at which the chips are transmitted and is twice the bit rate in Manchester and
Miller coding since these codes use two chips per bit (see chapter 14.7).
© Semtech 2006
fine and coarse: the division factors selected by RfifBRCoarse and RfifBRFine.
f
RCExt
: RC frequency or the half the external clock frequency.
output bitstream
output bitstream
Figure 14-7 : Output clock in Transmission mode
output clock
RfifBRFine[3:0]
Table 14-17 : Effect of RfifBRFine[3:0]
baudrate
0000
0001
0010
0011
1101
1110
1111
...
=
14-13
fine
Bi-Phase - Level
∗
NRZ - Level
coarse
f
RCExt
*
16
fine
14
15
16
...
1
2
3
4
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