Re: A89: Line 1111 Emulator


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Re: A89: Line 1111 Emulator




At 23:16 1998-12-28 -0500, you wrote:
>
>I have been getting the error message "Line 1111 Emulator" from a program that
>I wrote... the problem is that it's erratic. Sometimes it's there, sometimes
>it's not. What does this mean? I think that it might have to do with this
>line:
>
> lea 10(a7),a7

Nope, it has nothing to do with that line...

"Line 1111 Emulator" error is essentially the same thing as Illegal
Instruction.
The only difference is that Line 1111 Emulator error indicates that the illegal
instruction had the opcode Fxxx (1111 = F). There is similiar error, Line
1110 or something like that, which are opcodes starting with Exxx (or if it
was Dxxx, or Cxxx, or ...)

Why have a special error message for that? In some systems you want
to connect a coprocessor to the original processor. That processor
has it's own instructions, and thus have to be different from the 68k
instructions. To make this easier, there are some reserved opcodes, namely
the Fxxx opcodes. You can then trap the Line 1111 Emulator address, so
when a program uses a coprocessor instruction, the Line... caughts the opcode
and sends a signal to the coprocessor to perform whatever it is to do (most
likely just passing the remaining 12 bits of the opcode).

I hope this made sense :)

--
Real name:     Jimmy Mårdell         
Email:         mailto:yarin@acc.umu.se
Homepage:      http://www.acc.umu.se/~yarin/

Icarus Productions homepage: http://icarus.ganymed.org/


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