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.
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:
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.
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.
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.