LPC2420_60 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 6.2 — 16 October 2013 26 of 87
NXP Semiconductors
LPC2420/2460
Flashless 16-bit/32-bit microcontroller
7. Functional description
7.1 Architectural overview
The LPC2420/2460 microcontroller consists of an ARM7TDMI-S CPU with emulation
support, the ARM7 local bus for closely coupled, high-speed access to the majority of
on-chip memory, the AMBA AHB interfacing to high-speed on-chip peripherals and
external memory, and the AMBA APB for connection to other on-chip peripheral functions.
The microcontroller permanently configures the ARM7TDMI-S processor for little-endian
byte order.
The LPC2460 only implements two AHB in order to allow the Ethernet block to operate
without interference caused by other system activity. The primary AHB, referred to as
AHB1, includes the VIC, GPDMA controller, and EMC.
The second AHB (LPC2460 only), referred to as AHB2, includes only the Ethernet block
and an associated 16 kB SRAM. In addition, a bus bridge is provided that allows the
secondary AHB to be a bus master on AHB1, allowing expansion of Ethernet buffer space
into off-chip memory or unused space in memory residing on AHB1.
In summary, bus masters with access to AHB1 are the ARM7 itself, the GPDMA function,
and the Ethernet block (via the bus bridge from AHB2). Bus masters with access to AHB2
are the ARM7 and the Ethernet block.
AHB peripherals are allocated a 2 MB range of addresses at the very top of the 4 GB
ARM memory space. Each AHB peripheral is allocated a 16 kB address space within the
AHB address space. Lower speed peripheral functions are connected to the APB. The
AHB to APB bridge interfaces the APB to the AHB. APB peripherals are also allocated a
2 MB range of addresses, beginning at the 3.5 GB address point. Each APB peripheral is
allocated a 16 kB address space within the APB address space.
The ARM7TDMI-S processor is a general purpose 32-bit microprocessor, which offers
high performance and very low power consumption. The ARM architecture is based on
Reduced Instruction Set Computer (RISC) principles, and the instruction set and related
decode mechanism are much simpler than those of microprogrammed complex
instruction set computers. This simplicity results in a high instruction throughput and
impressive real-time interrupt response from a small and cost-effective processor core.
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 ARM7TDMI-S processor also employs a unique architectural strategy known as
Thumb, which makes it ideally suited to high-volume applications with memory
restrictions, or applications where code density is an issue.
The key idea behind Thumb is that of a super-reduced instruction set. Essentially, the
ARM7TDMI-S processor has two instruction sets:
• the standard 32-bit ARM set
• a 16-bit Thumb set
