
UM10800
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© NXP Semiconductors N.V. 2016. All rights reserved.
User manual
Rev. 1.2 — 5 October 2016
45 of 487
NXP Semiconductors
UM10800
Chapter 5: LPC82x System configuration (SYSCON)
U_PCLK = UARTCLKDIV/(1 + MULT/DIV).
UARTCLKDIV is the USART clock configured in the UARTCLKDIV register.
The fractional portion (1 + MULT/DIV) is determined by the two USART fractional divider
registers in the SYSCON block:
1. The DIV value programmed in this register is the denominator of the divider used by
the fractional rate generator to create the fractional component of U_PCLK.
2. The MULT value of the fractional divider is programmed in the UARTFRGMULT
register. See
Remark:
To use of the fractional baud rate generator, you must write 0xFF to this register
to yield a denominator value of 256. All other values are not supported.
See also:
Section 13.3.1 “Configure the USART clock and baud rate”
Section 13.7.1 “Clocking and baud rates”
5.6.20 USART fractional generator multiplier value register
All USART peripherals share a common clock U_PCLK, which can be adjusted by a
fractional divider:
U_PCLK = UARTCLKDIV/(1 + MULT/DIV).
UARTCLKDIV is the USART clock configured in the UARTCLKDIV register.
The fractional portion (1 + MULT/DIV) is determined by the two USART fractional divider
registers in the SYSCON block:
1. The DIV denominator of the fractional divider value is programmed in the
.
2. The MULT value programmed in this register is the numerator of the fractional divider
value used by the fractional rate generator to create the fractional component to the
baud rate.
See also:
Section 13.3.1 “Configure the USART clock and baud rate”
Section 13.7.1 “Clocking and baud rates”
Table 40.
USART fractional generator divider value register (UARTFRGDIV, address 0x4004
80F0) bit description
Bit
Symbol
Description
Reset
value
7:0
DIV
Denominator of the fractional divider. DIV is equal to the programmed
value +1. Always set to 0xFF to use with the fractional baud rate
generator.
0
31:8
-
Reserved
-