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UART Registers
19.5.1.34 Carrier Frequency Prescaler Register (CFPS)
Since the consumer IR (CIR) works at modulation rates of 30–56.8 kHz, the 48 MHz clock must be
prescaled before the clock can drive the IR logic. The carrier frequency prescaler register (CFPS) sets the
divisor rate to give a range to accommodate the remote control requirements in BAUD multiples of 12×.
The value of the CFPS at reset is 105 decimal (69h), which equates to a 38.1 kHz output from starting
conditions. The 48 MHz carrier is prescaled by the CFPS that is then divided by the 12× BAUD multiple.
The carrier frequency prescaler register (CFPS) is shown in Figure 19-67 and described in Table 19-65.
Figure 19-67. Carrier Frequency Prescaler Register (CFPS)
15 8 7 0
Reserved CFPS
R-0 R/W-69h
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 19-65. Carrier Frequency Prescaler Register (CFPS) Field Descriptions
Bit Field Value Description
15-8 Reserved 0 Reserved.
7-0 CFPS 0-FFh System clock frequency prescaler at (12× multiple). CFPS = 0 is not supported. Examples for CFPS
values:
Target Frequency (kHz) CFPS (decimal) Actual Frequency (kHz)
30 133 30.08
32.75 122 32.79
36 111 36.04
36.7 109 36.69
38 105 38.1
40 100 40
56.8 70 57.14
3535
SPRUH73H–October 2011–Revised April 2013 Universal Asynchronous Receiver/Transmitter (UART)
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