BSP Developer's Guide

VxWorks 5.5
BSP Developer’s Guide
4.3.1 RAM
VxWorks CISC processors require 1 MB of RAM for a development system that
includes all of the standard VxWorks features, such as the shell, network, file
system, loader, and others. RISC processors typically require more RAM space:
2 MB of RAM is the minimum; 4 MB is encouraged. For a scaled-down production
system, the amount of RAM required depends on the application size and the
options selected.
The primary configuration values controlling the usage of memory are
LOCAL_MEM_LOCAL_ADRS, LOCAL_MEM_SIZE, USER_RESERVED_MEM,
ROM_TEXT_ADRS, ROM_WARM_ADRS, and ROM_SIZE. For more information on
these values, see 2.2.1 BSP Source and Include Files, p.12.
4.3.2 ROM
VxWorks CISC processors require a minimum of 128 KB of ROM, which is just
sufficient for VxWorks compressed boot ROMs. RISC processors typically require
greater ROM space; 256 KB of ROM should be considered a minimum. These
figures do not include any ROM-resident application code.
Applications running out of ROM are usually slow because of 16-bit or (more
commonly) 8-bit data width, slow access times, and so on. VxWorks avoids this
problem by typically copying the contents of the boot ROMs into RAM.
For information on creating a ROM-resident VxWorks image, see the discussion of
executing VxWorks from ROM in the VxWorks Programmer’s Guide: Configuration,
and the Tornado User’s Guide: Cross-Development.
The configuration macros ROM_TEXT_ADRS and ROM_SIZE control the actual
usage of ROM memory space. For more information, see 2.2.1 BSP Source and
Include Files, p.12.
The macro ROM_WARM_ADRS is the warm boot entry point used by the
sysToMonitor( ) routine. It is normally defined as a constant offset, normally 8
bytes, above the cold boot entry point ROM_TEXT_ADRS.
4.3.3 Ethernet RAM
Some application designers have elected to provide dedicated pools of memory to
DMA-based Ethernet chips. CPU access to its own memory is therefore
unimpeded by incoming Ethernet packets, thus guaranteeing real-time response.
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