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Philips Semiconductors
Volume 1
1.5 Architectural overview
The LPC2131/2/4/6/8 consists of an ARM7TDMI-S CPU with emulation support, the
ARM7 Local Bus for interface to on-chip memory controllers, the AMBA Advanced
High-performance Bus (AHB) for interface to the interrupt controller, and the VLSI
Peripheral Bus (VPB, a compatible superset of ARM's AMBA Advanced Peripheral Bus)
for connection to on-chip peripheral functions. The LPC2131/2/4/6/8 configures the
ARM7TDMI-S processor in little-endian byte order.
AHB peripherals are allocated a 2 megabyte range of addresses at the very top of the
4 gigabyte ARM memory space. Each AHB peripheral is allocated a 16 kB address space
within the AHB address space. LPC2131/2/4/6/8 peripheral functions (other than the
interrupt controller) are connected to the VPB bus. The AHB to VPB bridge interfaces the
VPB bus to the AHB bus. VPB peripherals are also allocated a 2 megabyte range of
addresses, beginning at the 3.5 gigabyte address point. Each VPB peripheral is allocated
a 16 kB address space within the VPB address space.
The connection of on-chip peripherals to device pins is controlled by a Pin Connect Block
(see chapter "Pin Connect Block" on page 73). This must be configured by software to fit
specific application requirements for the use of peripheral functions and pins.
1.6 ARM7TDMI-S processor
The ARM7TDMI-S 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 THUMB set's 16-bit instruction length allows it to approach twice the density of
standard ARM code while retaining most of the ARM's performance advantage over a
traditional 16-bit processor using 16-bit registers. This is possible because THUMB code
operates on the same 32-bit register set as ARM code.
THUMB code is able to provide up to 65% of the code size of ARM, and 160% of the
performance of an equivalent ARM processor connected to a 16-bit memory system.
User manual
•
The standard 32-bit ARM instruction set.
•
A 16-bit THUMB instruction set.
Rev. 01 — 24 June 2005
UM10120
Chapter 1: Introductory information
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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