[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Opcode Instruction Question
- Subject: Re: Opcode Instruction Question
- From: judge_harsh_blues@hotmail.com (judge harsh)
- Date: 30 Apr 2002 19:51:08 -0700
- Newsgroups: comp.sys.apple2
- Organization: http://groups.google.com/
- References: <6IZy8.162363$XV5.15105967@bin4.nnrp.aus1.giganews.com>
- Xref: archiver1.google.com comp.sys.apple2:19204
> Opcode Instruction Question
>
> I know that 65816 microprocessor always has 256 opcode instructions
> while Intel microprocessor has more than 256 opcode instructions. For
> example, 65816 uses equal '=' for JMP, but Intel uses '=', '>', '<', '>=',
> and '<=' for JMP. It seems that it is not necessary to have extra JMP
> instructions.
it's a matter naming convention.
If we were to look at things from the intel perspective, the 816
actually has 4 jmp instructions:
bra -- jump to +- 128 byte offset
brl -- jump to +/- 32767 byte offset
jmp -- jump to absolute 16 bit address
jml -- jump to absolute 24 bit address.
Are all those extra JMP instructions "necessary"?
The intel JMPs do the above sort of thing, as well as jump to an
address specified in a register.