Re: Opcode Instruction Question

[dempson@actrix.gen.nz (David Empson)]

Linards Ticmanis <ticmanis@coli.uni-sb.de> wrote:

> Bryan Parkoff wrote:
> >     I understand now.  All 65xxx use only 8-bit for program status (P).  Is
> > it true that Intel x86 have 16-bit for program status, but you said it is
> > only 8-bit?
> >     Is it correct that 68K use 16-bit for program status?
> 
> The length of the operands has nothing to do with the length of the
> status word.

Another oddball processor I've encountered, though I haven't programmed
it (other people at work have done): the Atmel AVR family.

It is an 8-bit micro (probably with an 8-bit status register).  It has a
Harvard architecture with separate instruction and data address spaces.
The data space is addressed has 8 bits per memory location, while the
instruction space has 12 bits per memory location (using Flash memory
which is internal to the MCU).

The "opcode" in this case may be up to 12 bits, with operand data being
included in the first instruction word in some cases, or with additional
12-bit words being fetched for operand data in other cases.

-- 
David Empson
dempson@actrix.gen.nz