On 2013-08-02, Dennis Lee Bieber <[email protected]> wrote:
> On Thu, 1 Aug 2013 19:29:06 +0000 (UTC), Grant Edwards
><[email protected]> declaimed the following:
>
>>
>>I got tired of hand assembling (and disassembling) code for a custom
>>microprocessor, so I wrote an assembler and a disassembler.
>
> Let me know when you recreate XDS meta-symbol. It didn't even have the
> Sigma native instruction set built in, one had to specify the instruction
> set using a "system" directive. What it did have was a directive to define
> instruction formats (my manuals are in storage so this is pseudo-code).
>
> MOV opt,2,3,3 b'01',af(1),af(2)
>
> Which translates as: mnemonic is MOV, format is 2-bits, 3-bits, 3-bits,
> first field is binary 01, second field is argument field 1, third field is
> argument field 2.
That's pretty much how my assembler works. There is one variable
bit-width operand field in the opcode byte, and some instructions have
a single byte immediate operand following the opcode byte. Operands
can eitehr be absolute values or PC-relative offsets (in the case of
branch instructions).
--
Grant Edwards grant.b.edwards Yow! I hope the
at ``Eurythmics'' practice
gmail.com birth control ...
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