Datasheet
LPC540xx All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2018. All rights reserved.
Product data sheet Rev. 1.8 — 22 June 2018 61 of 168
NXP Semiconductors
LPC540xx
32-bit ARM Cortex-M4 microcontroller
7.10 System control
7.10.1 Clock sources
The LPC540xx supports one external and two internal clock sources:
• Free Running Oscillator (FRO).
• Watchdog oscillator (WDOSC).
• Crystal oscillator.
7.10.1.1 Free Running Oscillator (FRO)
The FRO 12 MHz oscillator provides the default clock at reset and provides a clean
system clock shortly after the supply pins reach operating voltage.
• 12 MHz internal FRO oscillator, factory trimmed for accuracy, that can optionally be
used as a system clock as well as other purposes.
• Selectable 48 MHz or 96 MHz FRO oscillator, factory trimmed for accuracy, that can
optionally be used as a system clock as well as other purposes.
7.10.1.2 Watchdog oscillator (WDOSC)
The watchdog oscillator is a low-power internal oscillator. The WDOSC can be used to
provide a clock to the WWDT and to the entire chip. The low-power watchdog oscillator
provides a selectable frequency in the range of 6 kHz to 1.5 MHz. The accuracy of this
clock is limited to 40% over temperature, voltage, and silicon processing variations.
Fig 10. LPC540xx APB Memory map
21-14
13
11-9
8
7-0
0x4003 6000
0x4002 D000
0x4002 C000
0x4002 9000
0x4002 8000
0x4002 0000
(reserved)
(reserved)
(reserved)
RIT
CTIMER2
APB bridge 1
20-15
14
13
12
11-10
9
8
0x4001 F000
0x4000 E000
0x4000 D000
0x4000 C000
0x4000 A000
0x4000 9000
0x4000 8000
0x4000 6000
0x4000 5000
0x4000 4000
0x4000 3000
0x4000 2000
0x4000 1000
0x4000 0000
(reserved)
MRT
(reserved)
CTIMER0
WDT
Micro-Tick
CTIMER1
APB bridge 0
7-6
5
4
3
2
1
Input muxes
GINT1
IOCON
Pin Interrupts (PINT)
(reserved)
GINT0
0
Syscon
31-10
9
8
7-1
0
0x4005 FFFF
0x4004 A000
0x4004 9000
0x4004 8000
0x4004 1000
0x4004 0000
(reserved)
CTIMER3
Asynch. Syscon
(reserved)
CTIMER4
Asynchronous APB bridge
aaa-029065
OTP controller
(reserved)
0x4001 FFFF
0x4001 5000
21
31-22
Smart card 0
Smart card 1
22
23
0x4001 6000
(reserved)
0x4003 7000
0x4003 8000
0x4003 FFFF
25-24
RTC
0x4002 E000
12
26
RNG
31-28
(reserved)
0x4003 A000
0x4003 B000
27
(reserved)
0x4003 C000