BSP Developer's Guide

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Hardware Guidelines
4.4.13 Parallel Ports
VxWorks provides simple support of parallel ports. Refer to directory
target/src/drv/parallel for supported devices and capabilities.
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4.5 Enabling the Virtual Memory Library
Before proceeding with this section, review the vmBaseLib and vmLib reference
entries and the VxWorks Programmer’s Guide: Virtual Memory Interface.
The vmBaseLib (the base virtual memory support library) and the vmLib (the
VxVMI Option) have similar BSP requirements. Because vmBaseLib is bundled
with VxWorks, BSPs are written to include it by default. If the VxVMI Option is
installed, the end user need only change INCLUDE_MMU_BASIC to
INCLUDE_MMU_FULL in target/config/bspname/config.h to include the unbundled
library in future builds.
The rest of this section describes the changes you must make in the sysLib.c file
and the config.h file for all supported targets with MMUs, and additional changes
you must make for SPARC targets.
! CAUTION: Due to a limitation in the current implementation of VxWorks, virtual
addresses must equal physical addresses when using 68K MMUs.
4.5.1 Changes to sysLib.c
Virtual memory support has two requirements:
■
Add a physical memory description. This requires the inclusion of one header
file and the definition of two variables. Start with the code example shown in
Example 4-1, and change it as appropriate.
– Local RAM is valid, writable, and cacheable. ROM is valid, read-only, and
often non-cached. I/O devices are valid, writable, and non-cached. If
applicable, VMEbus regions are valid, writable, and usually non-cached.
Flash ROM is usually writable and non-cached if it can be written directly
from the CPU.
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