The correct syntax for the GDB command function above is
define mtia
if $argc == 1 then
set $address = (unsigned char*)$arg0
while($address != $pc)
nexti
end
end
I had an asterisk in front of (unsigned char*). This removed the pointer type. This caused a syntax error with $address != $pc as $pc is considered a pointer.
This function performs a single assembly instruction step, until the address passed into the function is reached. Slow, but on the old M68332 CPU, this is all I have.