.OPT

Directive that changes assembler options. The only options allowed are:

Option name Importance
Proc6502 selecting the basic set of 6502 processor commands
Proc65c02 selecting an extended set of 65c02, 6501, and other processors.
Proc6501 Same as Proc65c02.
Proc65816 Select the 65816 processor.
CaseSensitive Differentiating lowercase and uppercase letters in label names
CaseInsensitive treated as equal lowercase and uppercase letters in label names
SwapBin swap binary radix @ and modulo % operators - % now becomes binary radix and @ becomes modulo.

Syntax:

    .OPT option_name { , option_name }

Example:

    .OPT Proc65c02, CaseInsensitive 
    .OPT Proc65816, CaseSensitive, SwapBin