Configuration

Configuration
	Chapter 252. Cogent CSB337 Board Support

Overview

The CSB337 platform HAL package is loaded automatically when eCos is configured for a csb337 target. It should never be necessary to load this package explicitly. Unloading the package should only happen as a side effect of switching target hardware.

Startup

The CSB337 platform HAL package supports three separate startup types:

RAM: This is the startup type which is normally used during application development. The board has RedBoot programmed into flash and boots into that initially. arm-eabi-gdb is then used to load a RAM startup application into memory and debug it. It is assumed that the hardware has already been initialized by RedBoot. By default the application will use the eCos virtual vectors mechanism to obtain certain services from RedBoot, including diagnostic output.
ROM: This startup type can be used for finished applications which will be programmed into flash at physical address 0x10000000. The application will be self-contained with no dependencies on services provided by other software. eCos startup code will perform all necessary hardware initialization.
ROMRAM: This startup type can be used for finished applications which will be programmed into flash at physical location 0x10000000. However, when it starts up the application will first copy itself to RAM at 0x00000000 and then run from there. RAM is generally faster than flash memory, so the program will run more quickly than a ROM-startup application. The application will be self-contained with no dependencies on services provided by other software. eCos startup code will perform all necessary hardware initialization.

RedBoot and Virtual Vectors

If the application is intended to act as a ROM monitor, providing services for other applications, then the configuration option CYGSEM_HAL_ROM_MONITOR should be set. Typically this option is set only when building RedBoot.

If the application is supposed to make use of services provided by a ROM monitor, via the eCos virtual vector mechanism, then the configuration option CYGSEM_HAL_USE_ROM_MONITOR should be set. By default this option is enabled when building for a RAM startup, disabled otherwise. It can be manually disabled for a RAM startup, making the application self-contained, as a testing step before switching to ROM startup.

If the application does not rely on a ROM monitor for diagnostic services then the serial port will be claimed for HAL diagnostics.

Flash Driver

The CBS337 board contains an 8Mb Intel StrataFlash flash device. The CYGPKG_DEVS_FLASH_STRATA package contains all the code necessary to support these parts and the CYGPKG_DEVS_FLASH_CSB337 package contains definitions that customize the driver to the CSB337 board.

Ethernet Driver

The CSB337 board uses the AT91RM9200's internal EMAC ethernet device attached to an external Intel LXT971 PHY. The CYGPKG_DEVS_ETH_ARM_AT91RM9200 package contains all the code necessary to support this device and the CYGPKG_DEVS_ETH_ARM_CSB337 package contains definitions that customize the driver to the CSB337 board.

System Clock

By default, the system clock interrupts once every 10ms, corresponding to a 100Hz clock. This can be changed by the configuration option CYGNUM_HAL_RTC_DENOMINATOR which corresponds to the clock frequency. Other clock-related settings are recalculated automatically if the denominator is changed.

Compiler Flags

The platform HAL defines the default compiler and linker flags for all packages, although it is possible to override these on a per-package basis. Most of the flags used are the same as for other architectures supported by eCos. There is just one flag specific to this port:

-mcpu=arm9: The arm-eabi-gcc compiler supports many variants of the ARM architecture. A -m option should be used to select the specific variant in use, and with current tools -mcpu=arm9 is the correct option for the ARM920T CPU in the AT91RM9200.


Setup		The HAL Port

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