UM10850
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User manual
Rev. 2.4 — 13 September 2016
258 of 464
NXP Semiconductors
UM10850
Chapter 21: LPC5410x USARTs (USART0/1/2/3)
The USART can also be clocked by the 32 kHz RTC oscillator. Set the MODE32K bit to
enable this 32 kHz mode. See also
Section 21.7.1.4 “32 kHz mode”
.
For details on the clock configuration see:
Section 21.7.1 “Clocking and baud rates”
21.3.2 Configure the USART for wake-up
A USART can wake up the system from sleep mode in asynchronous or synchronous
mode on any enabled USART interrupt.
In Deep-sleep or power-down mode, there are two options for configuring USART for
wake-up:
•
If the USART is configured for synchronous slave mode, the USART block can create
an interrupt on a received signal even when the USART block receives no on-chip
clocks - that is in Deep-sleep or Power-down mode.
As long as the USART receives a clock signal from the master, it can receive up to
one byte in the RXDAT register while in Deep-sleep or Power-down mode. Any
interrupt raised as part of the receive data process can then wake up the part.
•
If the 32 kHz mode is enabled, the USART can run in asynchronous mode using the
32 kHz RTC oscillator and create interrupts.
21.3.2.1 Wake-up from Sleep mode
•
Configure the USART in either asynchronous mode or synchronous mode. See
•
Enable the USART interrupt in the NVIC.
•
Any USART interrupt wakes up the part from sleep mode. Enable the USART
interrupt in the INTENSET register (
).
Fig 43. USART clocking
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