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.
