This documentation explains how the eCos HAL specification has been
mapped onto the CSB337 hardware, and should be read in conjunction
with that specification. The CSB337 platform HAL package complements
the ARM architectural HAL and the ARM9 variant HAL. It provides
functionality which is specific to the target board.
Startup
Following a hard or soft reset the HAL will initialize or
reinitialize most of the on-chip peripherals. There is an exception
for RAM startup applications which depend on a ROM monitor for certain
services.
For ROM or ROMRAM startup, the HAL will perform additional
initialization, setting up the external RAM and programming the
various internal registers. This is all done in the
PLATFORM_SETUP1 macro in the assembler
header file hal_platform_setup.h.
Linker Scripts and Memory Maps
The platform HAL package provides the memory layout information needed
to generate the linker script. The key memory locations are as follows:
Flash
This is located at address 0x10000000 of the physical memory space.
However, the HAL uses the MMU to relocate it to virtual
address 0x60000000 after initialization.
SDRAM
This is located at address 0x20000000 of the physical memory
space. However the HAL uses the MMU to relocate this to virtual
address 0x00000000. The same memory is also accessible uncached and
unbuffered at virtual location 0x20000000 for use by devices. The
first 32 bytes are used for hardware exception vectors. The next 32
bytes are used for the VSR table and the next 256 bytes are normally
used for the eCos virtual vectors, allowing RAM-based applications to
use services provided by the ROM monitor. For ROM/ROMRAM startup, all
remaining SDRAM is available. For RAM startup, available RAM starts at
virtual location 0x00040000, with the bottom 256kB reserved for use by
RedBoot.
On-chip SRAM
This is located at address 0x00200000 of the physical memory
space. However the HAL uses the MMU to relocate this to virtual
address 0x70000000. The same memory is also accessible uncached and
unbuffered at virtual location 0x70100000 for use by devices. At
present this memory is entirely reserved for use by the ethernet
interface, since there are problems using external SDRAM for ethernet
buffers.
On-chip Peripheral Registers
These are located at address 0xFF000000 in the physical memory
space. When the MMU is enabled, it sets up a direct, uncached,
unbuffered mapping so that these registers remain accessible
at their physical locations.
Off-chip Peripherals
Apart from the SDRAM, flash and ethernet PHY, eCos does not currently
make any use of the off-chip peripherals present on the
CSB337.
Other Issues
The CSB337 platform HAL does not affect the implementation of other
parts of the eCos HAL specification. The ARM9 variant HAL, and the ARM
architectural HAL documentation should be consulted for further
details.
