Memory Map Concepts And Operating Modes 12 Memory Re-Mapping - Philips LPC213 Series User Manual

Philips Semiconductors
Volume 1
2.2.2 Memory re-mapping
In order to allow for compatibility with future derivatives, the entire Boot Block is mapped
to the top of the on-chip memory space. In this manner, the use of larger or smaller flash
modules will not require changing the location of the Boot Block (which would require
changing the Boot Loader code itself) or changing the mapping of the Boot Block interrupt
vectors. Memory spaces other than the interrupt vectors remain in fixed locations.
Figure 6
The portion of memory that is re-mapped to allow interrupt processing in different modes
includes the interrupt vector area (32 bytes) and an additional 32 bytes, for a total of
64 bytes. The re-mapped code locations overlay addresses 0x0000 0000 through
0x0000 003F. A typical user program in the Flash memory can place the entire FIQ
handler at address 0x0000 001C without any need to consider memory boundaries. The
vector contained in the SRAM, external memory, and Boot Block must contain branches to
the actual interrupt handlers, or to other instructions that accomplish the branch to the
interrupt handlers.
There are three reasons this configuration was chosen:
Re-mapped memory areas, including the Boot Block and interrupt vectors, continue to
appear in their original location in addition to the re-mapped address.
Details on re-mapping and examples can be found in
control" on page
User manual
shows the on-chip memory mapping in the modes defined above.
1. To give the FIQ handler in the Flash memory the advantage of not having to take a
memory boundary caused by the remapping into account.
2. Minimize the need to for the SRAM and Boot Block vectors to deal with arbitrary
boundaries in the middle of code space.
3. To provide space to store constants for jumping beyond the range of single word
branch instructions.
25.
Rev. 01 — 24 June 2005
UM10120
Chapter 2: Memory map
Section 3.6 "Memory mapping
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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