This documentation explains how the eCos HAL specification has been
mapped onto the MX1ADS/A hardware, and should be read in conjunction
with that specification. The MX1ADS/A 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
the on-chip peripherals that it uses. 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.
For SRAM startup, minimal initialization is performed, and it is
assumed that the JTAG device has initialized the hardware as described
earlier.
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:
SDRAM
This is located at address 0x08000000 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 0x04000000 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.
In the SRAM startup configuration, the SDRAM remains at its physical
address of 0x08000000, since the MMU is not enabled.
Flash
This is located at address 0x10000000 of the physical memory space.
It is mapped by the HAL using the MMU to the same virtual address with
caching and the write buffer enabled.
On-chip Peripheral Registers
These are located at address 0x00200000 in the physical memory
space. When the MMU is enabled, it sets up a direct, uncached,
unbuffered mapping for these at 0xA0000000 in the virtual address
space.
All hardware addresses in mc9328mxl.h give the
physical address. To use these, the macro
CYGARC_VIRTUAL_ADDRESS() should be applied to
these. This will yield the correct address depending on the startup
type.
Ethernet MAC
The Cirrus Logic CS8900A is addressed by Chip Select 4, and is located
at physical address 0x15000000. It is mapped uncached and
unbuffered to the same virtual address when the MMU is enabled.
Other Issues
The MX1ADS/A 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.
