Configuration

Name

Configuration -- Platform-specific Configuration Options

Overview

The evba7 platform HAL package is loaded automatically when eCos is configured for a evba7 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 evba7 platform HAL package supports two separate startup types:

RAM

This is the startup type which is normally used during application development. The board has the GDB stubrom or RedBoot programmed into flash at location 0x0 in internal on-chip Flash and boots from that location. 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 the ROM monitor. By default the application will use the eCos virtual vectors mechanism to obtain certain services from the ROM monitor, including diagnostic output.

ROM

This startup type can be used for finished applications which will be programmed into internal flash at location 0x0. The application will be self-contained with no dependencies on services provided by other software. eCos startup code will perform all necessary hardware initialization.

The ROM Monitor 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 the GDB Stubrom or 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, or as a testing step before switching to ROM startup.

If the application does not rely on a ROM monitor for diagnostic services then serial port UART0 will be claimed for HAL diagnostics.

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. The PLL multipliers and dividers may be configured to allow a core clock (CCLK) speed of up to 60MHz. The description of the clock-related CDL options may be found in the LPC2xxx variant HAL documentation.

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.

However there are two flags that are used if Thumb mode is to be supported:

-mthumb

The arm-eabi-gcc compiler will compile C and C++ files into the Thumb instruction set when this option is used.

-mthumb-interwork

This option allows programs to be created that mix ARM and Thumb instruction sets. Without this option, some memory can be saved. This option should be used if -mthumb is used.

2017-02-09
Documentation license for this page: eCosPro License