To use the binutils assembler, get the source from http://sources.redhat.com/pub/binutils/releases or from CVS.

To configure it for the C54x
./configure --target=c54x --prefix=/usr

Note: --prefix=/usr is where to put the compiled binaries is not required, the default value is /usr/local . However many systems by default don't have /usr/local/bin in the path (though I wish they did).

then do:
make
make install

This will create the binutils binaries with prefix names of c54x- so that they won't conflict with other files.
c54x-addr2line c54x-c++filt c54x-nm c54x-ranlib c54x-strings c54x-ar c54x-gasp c54x-objcopy c54x-readelf c54x-strip c54x-as c54x-ld c54x-objdump c54x-size
The important one is c54x-as. Man pages with the same names are also generated.

To compile the test code:
c54x-as -o test1.o test1.asm
c54x-ld test1.o -o test1.out