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2014-07-02 - Gecko Family - d0001_Rev1.30
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a parity bit is inserted to make the number of high bits (data + parity) even. If odd parity is chosen, the
parity bit makes the total number of high bits odd. When parity bits are disabled, which is the default
configuration, the parity bit is omitted.
Table 18.1. LEUART Parity Bit
PARITY [1:0]
Description
00
No parity (default)
01
Reserved
10
Even parity
11
Odd parity
See Section 18.3.5.4 (p. 255) for more information on parity bit handling.
18.3.2 Clock Source
The LEUART clock source is selected by the LFB bit field the CMU_LFCLKSEL register. The clock is
prescaled by the LEUARTn bitfield in the CMU_LFBPRESC0 register and enabled by the LEUARTn bit
in the CMU_LFBCLKEN0.
To use this module, the LE interface clock must be enabled in CMU_HFCORECLKEN0, in addition to
the module clock.
18.3.3 Clock Generation
The LEUART clock defines the transmission and reception data rate. The clock generator employs a
fractional clock divider to allow baud rates that are not attainable by integral division of the 32.768 kHz
clock that drives the LEUART.
The clock divider used in the LEUART is a 12-bit value, with a 7-bit integral part and a 5-bit fractional
part. The baud rate of the LEUART is given by :
LEUART Baud Rate Equation
br = fLEUARTn/(1 + LEUARTn_CLKDIV/256)
(18.1)
where fLEUARTn is the clock frequency supplied to the LEUART. The value of LEUARTn_CLKDIV thus
defines the baud rate of the LEUART. The integral part of the divider is right-aligned in the upper 24
bits of LEUARTn_CLKDIV and the fractional part is left-aligned in the lower 8 bits. The divider is thus a
256th of LEUARTn_CLKDIV as seen in the equation.
For a desired baud rate br
DESIRED
, LEUARTn_CLKDIV can be calculated by using:
LEUART CLKDIV Equation
LEUARTn_CLKDIV = 256 x (fLEUARTn/br
DESIRED
- 1)
(18.2)
Table 18.2 (p. 252) lists a set of desired baud rates and the closest baud rates reachable by the
LEUART with a 32.768 kHz clock source. It also shows the average baud rate error.
Summary of Contents for EFM32G
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