LPC540xx
NXP Semiconductors
32-bit ARM Cortex-M4 microcontroller
7. Functional description
7.1 Architectural overview
The ARM Cortex-M4 includes three AHB-Lite buses: the system bus, the I-code bus, and
the D-code bus. The I-code and D-code core buses allow for concurrent code and data
accesses from different slave ports.
The LPC540xx uses a multi-layer AHB matrix to connect the ARM Cortex-M4 buses and
other bus masters to peripherals in a flexible manner that optimizes performance by
allowing peripherals that are on different slave ports of the matrix to be accessed
simultaneously by different bus masters.
7.2 ARM Cortex-M4 processor
The ARM Cortex-M4 is a general purpose, 32-bit microprocessor, which offers high
performance and very low power consumption. The ARM Cortex-M4 offers many new
features, including a Thumb-2 instruction set, low interrupt latency, hardware multiply and
divide, interruptable/continuable multiple load and store instructions, automatic state save
and restore for interrupts, tightly integrated interrupt controller with wake-up interrupt
controller, and multiple core buses capable of simultaneous accesses.
A 3-stage pipeline is employed so that all parts of the processing and memory systems
can operate continuously. Typically, while one instruction is being executed, its successor
is being decoded, and a third instruction is being fetched from memory.
7.3 ARM Cortex-M4 integrated Floating Point Unit (FPU)
The FPU fully supports single-precision add, subtract, multiply, divide, multiply and
accumulate, and square root operations. It also provides conversions between fixed-point
and floating-point data formats, and floating-point constant instructions.
The FPU provides floating-point computation functionality that is compliant with the
ANSI/IEEE Std 754-2008, IEEE Standard for Binary Floating-Point Arithmetic, referred to
as the IEEE 754 standard.
7.4 Memory Protection Unit (MPU)
The Cortex-M4 includes a Memory Protection Unit (MPU) which can be used to improve
the reliability of an embedded system by protecting critical data within the user
application.
The MPU allows separating processing tasks by disallowing access to each other's data,
disabling access to memory regions, allowing memory regions to be defined as read-only
and detecting unexpected memory accesses that could potentially break the system.
The MPU separates the memory into distinct regions and implements protection by
preventing disallowed accesses. The MPU supports up to eight regions each of which can
be divided into eight subregions. Accesses to memory locations that are not defined in the
MPU regions, or not permitted by the region setting, will cause the Memory Management
Fault exception to take place.
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
56 of 168
NXP [ NXP ]
