This documentation explains how the eCos HAL specification has
been mapped onto the ADS512101 hardware, and should be read in
conjunction with that specification. The ADS512101 platform HAL
package complements the PowerPC architectural HAL and the MPC51XX
variant HAL. It provides functionality which is specific to the
Following a hard or soft reset the HAL will initialize or
reinitialize the on-chip peripherals that eCos uses. There is an
exception for RAM startup applications which depend on a ROM
monitor for certain services.
For ROM startup, the HAL will perform additional initialization,
setting up the external RAM and programming the various internal
registers. This is all done in the
hal_hardware_init function in the assembler
source file ads512101.S.
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
This is located at address 0xFC000000 of the physical memory
space. It is mapped by the BAR registers 1-1 to virtual address
0xFC000000 with caching enabled, and to 0x50000000 with caching
disabled. The PowerPC reset vector is at 0xFFF00100 so RedBoot
is normally programmed from 0xFFF00000.
This is located at address 0x00000000 of the physical memory
space. The first 0x3000 bytes are used for the exception entry
trampolines. The following 512 bytes contain 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 and JTAG startup, all
remaining SDRAM is available. For RAM startup, available RAM
starts at location 0x00100000, with the bottom 1MiB reserved
for use by RedBoot. The SDRAM is mapped 1-1 with cache enabled
at virtual address 0x00000000 and uncached at 0x20000000.
The 128KiB of on-chip SRAM is mapped 1-1 at 0x30000000. This
memory is not used by eCos and is therefore available for
All on-chip peripherals are accessed relative to the address in
the IMMBAR register. Both the PEEDI configuration file and eCos
itself set this to 0xE0000000. The CPLD is mapped to 0xE2000000
and is accessible just beyond the IMMBAR peripherals.
The tm_basic kernel test gives statistics gathered about the real-time
characterization and performance of the kernel. The sample output is shown here
The ADS512101 platform HAL does not affect the implementation of
other parts of the eCos HAL specification. The MPC55XX variant
HAL, and the PowerPC architectural HAL documentation should be
consulted for further details.