eCos Reference Manual
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# Configuration

## Name

Configuration -- Platform-specific Configuration Options

## Overview

The MicroDev platform HAL package is loaded automatically when eCos is configured for an `sh4_202_md` 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 MicroDev platform HAL package supports two separate startup types:

RAM

  This is the startup type which is normally used during application development. The board has RedBoot programmed into flash at location 0xA0000000 and boots from that location. sh-elf-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 location 0xA0000000. 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 MicroDev board contains 32Mb of Intel StrataFlash, specifically, two E28F128 parts in parallel. The `CYGPKG_DEVS_FLASH_STRATA` package contains all the code necessary to support these parts and the `CYGPKG_DEVS_FLASH_SH_MICRODEV` package contains definitions that customize the driver to the MicroDev board.

Note that if booting from EEPROM instead of flash, the flash driver will not be able to detect or use the flash parts.

## Ethernet Driver

The MicroDev board contains an SMSC LAN91C111 ethernet device. The `CYGPKG_DEVS_ETH_SMSC_LAN91CXX` package contains all the code necessary to support this part and the `CYGPKG_DEVS_ETH_SH_MICRODEV` package contains definitions that customize the driver to the MicroDev 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 are two flags specific to this port:

`-m4`

  The sh-elf-gcc compiler supports many variants of the SH architecture, from the SH2 onwards. A `-m` option should be used to select the specific variant in use, and with current tools `-m4` is the correct option for the SH4-202.

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