XR88C681CP Datasheet, PDF (56/99 Pages) Exar Corporation – CMOS DUAL CHANNEL UART (DUART)

XR88C681
Register

 $ -(% "


 $ -(% "


 $ -(% *"
*

 $ -(% *"
*
Contents
=_/
_/
 _/
*_/
Resulting Action
 ! *0 ' 2! $ *( 5 J 

 ! *0 ' 2! $ *( 5 J 
 ! *0 ' 2! $ *( 5 J 

 ! *0 ' 2! $ *( 5 J 
Table 19. Command Register Controls Over the Extend Bit
Note: If the user programs either nibble of the Clock Select Register (CSRn[7:4] or CSRn[3:0]) with values ranging from 016 to C16,
then the user is using the BRG as a source for timing. However, these standard bit rates (presented in Table 18) apply only if
the X1/CLK pin is driven with a 3.6864 MHz signal. If a signal with a different frequency (fo) is applied to the X1/CLK pin, then
the DUART channel is running at the following baud rate:
Actual Baud Rate =
N / *$  ;O R +
1/=/< 8I
provided that fo is between 2.0 MHz and 4.0 MHz.
Additionally, as in the case for standard baud rates, the actual frequency of the clock signal will be 16 times these values.
1X vs 16X Clock Signals
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'3D  $ C/5
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Figure 29. Example of a Serial Data
Transmission System
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