Hullo Jos Croeze, hope you are having a nice day!!
16-Mar-98 01:12:59, Jos Croeze wrote to Fernando Ariel Gont
          Subject: Problem to make a compiler
 FA>> Well, I don't know how to code the "jmp" instruction, as I don't
 FA>> have the address that equals "yeah" label.
 JC> Just teasing you a bit with my following comment. Have you noticed
 JC> that there are several opcodes for a jmp? If a jmp is closer than
Yeah, but I don't want to make a x86 compiler... I want to make a 6809
one..
I haven't studied very much how the 6809 instructions are encoded, but I
think (and hope), that it won't be very-very hard....
 JC> 7fh bytes you can use tw bytes for the opcode with the offset. If
 JC> the jmp is closer than 7fffh bytes you'll need three bytes (opcode
 JC> and two bytes for offset). And then there is a jmp-opcode followed
 JC> by two bytes, defining the direct address.
 JC> Writing .COM-files is easy when you use a direct address for every
 JC> jmp. In that case you just compile(assemble) the mnemonic to
 JC> opcodes, collecting the addresses op the labels.
As the program is stored in an EPROM, PROM or ROM, there are no "formats"
such as .COM...
I think the "structure" of a program is similar to that of a .COM, but, as
they are different uP's and systems, I'll have to study it...
Thanks, anyway!
 -=> Yours sincerely, Fernando Ariel Gont <=-
e-mail: FGont@siscor.bibnal.edu.ar
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