UM10360 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
User manual Rev. 3 — 19 December 2013 10 of 841
NXP Semiconductors
UM10360
Chapter 1: LPC176x/5x Introductory information
1.6 Architectural overview
The ARM Cortex-M3 includes three AHB-Lite buses, one system bus and the I-code and
D-code buses which are faster and are used similarly to TCM interfaces: one bus
dedicated for instruction fetch (I-code) and one bus for data access (D-code). The use of
two core buses allows for simultaneous operations if concurrent operations target different
devices.
The LPC176x/5x uses a multi-layer AHB matrix to connect the Cortex-M3 buses and other
bus masters to peripherals in a flexible manner that optimizes performance by allowing
peripherals on different slaves ports of the matrix to be accessed simultaneously by
different bus masters. Details of the multilayer matrix connections are shown in Figure 2
.
APB peripherals are connected to the CPU via two APB busses using separate slave
ports from the multilayer AHB matrix. This allows for better performance by reducing
collisions between the CPU and the DMA controller. The APB bus bridges are configured
to buffer writes so that the CPU or DMA controller can write to APB devices without
always waiting for APB write completion.
1.7 ARM Cortex-M3 processor
The ARM Cortex-M3 is a general purpose 32-bit microprocessor, which offers high
performance and very low power consumption. The Cortex-M3 offers many new features,
including a Thumb-2 instruction set, low interrupt latency, hardware divide,
interruptible/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.
Pipeline techniques are 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.
The ARM Cortex-M3 processor is described in detail in the Cortex-M3 User Guide that is
appended to this manual.
1.7.1 Cortex-M3 Configuration Options
The LPC176x/5x uses the r2p0 version of the Cortex-M3 CPU, which includes a number
of configurable options, as noted below.
System options:
• The Nested Vectored Interrupt Controller (NVIC) is included. The NVIC includes the
SYSTICK timer.
• The Wake-up Interrupt Controller (WIC) is included. The WIC allows more powerful
options for waking up the CPU from reduced power modes.
• A Memory Protection Unit (MPU) is included.
• A ROM Table in included. The ROM Table provides addresses of debug components
to external debug systems.
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