PXD20RM Datasheet, PDF (1031/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

27.12.3 Fractional baud rate generation
The baud rates for the receiver and transmitter are both set to the same value as programmed in the
Mantissa (LINIBRR) and Fraction (LINFBRR) registers.
Tx/Rx baud =
f_{ipg_clock_lin}
(16 * LFDIV)
LFDIV is an unsigned fixed point number. The 20-bit mantissa is coded in the LINIBRR register and the
fraction is coded in the LINFBRR register.
The following examples show how to derive LFDIV from LINIBRR and LINFBRR register values:
Example 27-1.
If LINIBRR = 27d and LINFBRR = 12d, then
Mantissa (LFDIV) = 27d
Fraction (LFDIV) = 12/16 = 0.75d
Therefore LFDIV = 27.75d
Example 27-2.
To program LFDIV = 25.62d,
LINFBRR = 16 * 0.62 = 9.92, nearest real number 10d = Ah
LINIBRR = mantissa(25.620d) = 25d = 19h
NOTE
The Baud Counters are updated with the new value of the Baud Registers
after a write to LINIBRR. Hence the Baud Register value must not be
changed during a transaction. The LINFBRR (containing the Fraction bits)
must be programmed before LINIBRR.
NOTE
LFDIV must be greater than or equal to 1.5d, for example, LINIBRR = 1
and LINFBRR = 8. Therefore, the maximum possible baudrate is
fperiph_set_1_clk / 24.
27.13 Programming considerations
This section describes the various configurations in which the LINFlexD can be used.
Freescale Semiconductor
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
27-75