
UM10800
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© NXP Semiconductors N.V. 2016. All rights reserved.
User manual
Rev. 1.2 — 5 October 2016
27 of 487
5.1 How to read this chapter
The system configuration block is identical for all LPC820 parts.
5.2 Features
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Clock control
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Configure the system PLL.
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Configure system oscillator and watchdog oscillator.
–
Enable clocks to individual peripherals and memories.
–
Configure clock output.
–
Configure clock dividers, digital filter clock, and USART baud rate clock.
•
Monitor and release reset to individual peripherals.
•
Select pins for external pin interrupts and pattern match engine.
•
Configuration of reduced power modes.
•
Wake-up control.
•
BOD configuration.
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MTB trace start and stop.
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Interrupt latency control.
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Select a source for the NMI.
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Calibrate system tick timer.
5.3 Basic configuration
Configure the SYSCON block as follows:
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The SYSCON uses the CLKIN, CLKOUT, RESET, and XTALIN/OUT pins. Configure
the pin functions through the switch matrix. See
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No clock configuration is needed. The clock to the SYSCON block is always enabled.
By default, the SYSCON block is clocked by the IRC.
5.3.1 Set up the PLL
The PLL creates a stable output clock at a higher frequency than the input clock. If you
need a main clock with a frequency higher than the 12 MHz IRC clock, use the PLL to
boost the input frequency.
1. Power up the system PLL in the PDRUNCFG register.
Section 5.6.33 “Power configuration register”
2. Select the PLL input in the SYSPLLCLKSEL register. You have the following input
options:
UM10800
Chapter 5: LPC82x System configuration (SYSCON)
Rev. 1.2 — 5 October 2016
User manual