m68k-m5272c3.html
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><H1
><A
NAME="M68K-M5272C3"
></A
>Overview</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN19375"
></A
><H2
>Name</H2
>eCos Support for the Freescale M5272C3 Board -- Overview</DIV
><DIV
CLASS="REFSECT1"
><A
NAME="M68K-M5272C3-DESCRIPTION"
></A
><H2
>Description</H2
><P
>The Freescale M5272C3 board has an MCF5272 ColdFire processor, 4MB of
external SDRAM, 2MB of external flash memory, and connectors plus
required support chips for all the on-chip peripherals. By default the
board comes with its own dBUG ROM monitor, located in the bottom half
of the flash.
</P
><P
>For typical eCos development a RedBoot image is programmed into the
top half of the flash memory, and the board is made to boot this image
rather than the existing dBUG monitor. RedBoot provides gdb stub
functionality so it is then possible to download and debug eCos
applications via the gdb debugger. This can happen over either a
serial line or over ethernet.
</P
></DIV
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CLASS="REFSECT1"
><A
NAME="M68K-M5272C3-HARDWARE"
></A
><H2
>Supported Hardware</H2
><P
>In a typical setup the bottom half of the flash memory is reserved for
the dBUG ROM monitor and is not accessible to eCos. That leaves four
flash blocks of 256K each. Of these one is used for the RedBoot image
and another is used for managing the flash and holding RedBoot fconfig
values. The remaining two blocks at 0xFFF40000 and 0xFFF80000 can be
used by application code.
</P
><P
>By default eCos will only support the four megabytes of external SDRAM
present on the initial versions of the board, accessible at location
0x00000000. Later versions come with 16MB. If all 16MB of memory are
required then the ACR0 register needs to be changed. The default value
is controlled by the configuration option
<CODE
CLASS="VARNAME"
>CYGNUM_HAL_M68K_M5272C3_ACR0</CODE
>, but this option is
only used during ROM startup so in a typical setup it would be
necessary to rebuild and update RedBoot. Alternatively the register
can be updated by application code, preferably using a high priority
static constructor to ensure that the extra memory is visible before
any code tries to use that memory. It will also be necessary to change
the memory layout so that the linker knows about the additional
memory.
</P
><P
>By default the 4K of internal SRAM is mapped to location 0x20000000
using the RAMBAR register. This is not used by eCos or by RedBoot so
can be used by application code. The M68K architectural HAL has an
<TT
CLASS="FILENAME"
>iram1.c</TT
> testcase to illustrate the linker script
support for this. The internal 16K of ROM is left
disabled by default because its contents are of no use to most
applications. The on-chip peripherals are mapped at 0x10000000 via the
MBAR register.
</P
><P
>There is a serial driver <CODE
CLASS="VARNAME"
>CYGPKG_DEVS_SERIAL_MCFxxxx</CODE
>
which supports both on-chip UARTs. One of the UARTs, usually uart0,
can be used by RedBoot for communication with the host. If this UART
is needed by the application, either directly or via the serial
driver, then it cannot also be used for RedBoot communication. Another
communication channel such as ethernet should be used instead. The
serial driver package is loaded automatically when configuring for the
M5272C3 target.
</P
><P
>There is an ethernet driver <CODE
CLASS="VARNAME"
>CYGPKG_DEVS_ETH_MCFxxxx</CODE
>
for the on-chip ethernet device. This driver is also loaded
automatically when configuring for the M5272C3 target. The M5272C3
board does not have a unique MAC address, so a suitable address has to
be programmed into flash via RedBoot's <B
CLASS="COMMAND"
>fconfig</B
>
command.
</P
><P
>eCos manages the on-chip interrupt controller. Timer 3 is used to
implement the eCos system clock, but timers 0, 1 and 2 are unused and
left for the application. The GPIO pins are manipulated only as needed
to get the UARTs and ethernet working. eCos will reset the remaining
on-chip peripherals (DMA, USB, PLCI, QSPI and PWM) during system
startup or soft reset but will not otherwise manipulate them.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="M68K-M5272C3-TOOLS"
></A
><H2
>Tools</H2
><P
>The M5272C3 port is intended to work with GNU tools configured for an
m68k-elf target. The original port was done using m68k-elf-gcc version
3.2.1, m68k-elf-gdb version 5.3, and binutils version 2.13.1.
</P
><P
>By default eCos is built using the compiler flag
<CODE
CLASS="OPTION"
>-fomit-frame-pointer</CODE
>. Omitting the frame pointer
eliminates some work on every function call and makes another register
available, so the code should be smaller and faster. However without a
frame pointer m68k-elf-gdb is not always able to identify stack
frames, so it may be unable to provide accurate backtrace information.
Removing this compiler flag from the configuration option
<CODE
CLASS="VARNAME"
>CYGBLD_GLOBAL_CFLAGS</CODE
> avoids such debug problems.
</P
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