I’m getting closer to being able to run code on the MC68008 system I’m building. I’ve designed glue logic (using two 22V10 GALs and an 74hct138 3-to-8 decoder) for address decoding, DTACK generation, and interrupt logic. (Actually, the interrupt logic GAL is mostly unused, since I don’t yet have an interrupt-generating device in the circuit.) I’ve also added a 27C512 EPROM and a 74ls374 output port to the circuit. (Schematics and photos soon.) My goal is to burn an EPROM that will cause an LED connected to the output port to blink. That, of course, requires that I have some way of writing code to burn onto the EPROM!

I thought about hand-assembling a short program, but in the end I decided to build a cross-development toolchain using GNU binutils and gcc.

Here are the magic incantations I used (save this as a file called build.sh):

set -e
export M68KPREFIX=/home/dhovemey/linux/m68k-elf
export PATH=$M68KPREFIX/bin:$PATH
mkdir crossgcc
wget http://ftp.gnu.org/gnu/binutils/binutils-2.23.tar.gz
gunzip -c binutils-2.23.tar.gz | tar xvf -
wget http://ftp.gnu.org/gnu/gcc/gcc-4.4.2/gcc-core-4.4.2.tar.bz2
bunzip2 -c gcc-core-4.4.2.tar.bz2 | tar xvf -
mkdir build
cd build
mkdir binutils
mkdir gcc
cd binutils
../../binutils-2.23/configure --target=m68k-unknown-elf --prefix=$M68KPREFIX
make -j 3
make install
cd ../gcc
../../gcc-4.4.2/configure --target=m68k-unknown-elf --disable-libssp \
make -j 3
make install

You can change the value of M68KPREFIX to whatever directory you’d like to install the toolchain in. You can also change the -j 3 flag on the make commands. I have a CPU with 3 cores, which is why I used that particular value.

Execute using the command

sh build.sh

in some scratch directory.

You may find that various development packages (such as libgmp-dev) must be installed before the build will succeed.

Note that all of the tools will be prefixed with m68k-unknown-elf-. So, for example, gcc is m68k-unknown-elf-gcc.

I used the latest version of binutils, but an older version of gcc, based on a gcc bug report that happens to mention a specific configure command for gcc 4.4.2 that builds an m68k/elf embedded target. Binutils is generally very straightforward to compile for an embedded target, but gcc is usually more complicated, so it was useful to start with a known-good configure command.

I have only tested binutils (as, ld, objcopy, and objdump) so far; I’m hoping that the C compiler will work as well, although it will be a while before I’m at the point where I will be trying to execute C code.

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