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millfork/docs/various/asmdiff.md
Karol Stasiak 8ec82ef520 6809: Document direct addressing mode
2020-07-31 01:57:10 +02:00

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Differences in assembly

Syntax

  • High and low bytes of an 16-bit value are acquired using the hi and lo functions, not the > and < operators.

  • Anonymous labels and local labels are not supported.
    All labels defined in assembly are global.
    Colons are required in label declarations.

  • Macros are inserted using the + operator.

  • Raw bytes are inserted using the Millfork array syntax, not with any pseudoopcode (like !byte, db or fcb)

  • Assembly blocks cannot contain definitions of constants or variables.

  • 6502: To enforce zero-page addressing, wrap the argument in the lo function: lo(arg)

  • 6502: To enforce absolute addressing, add a 16-bit zero to the argument: 0000 + arg

  • GameBoy: The $FF page loads/stores are written LDH (C),A, not LD ($FF00+C),A.

  • GameBoy: The loads/stores that postincrement/postdecrement HL write the HL register as HLI or HLD, not HL+ or HL-

  • Z80: Indexing using the index register uses the IX(1) syntax, not (IX+1) or 1(IX).

  • Z80: Most undocumented instructions are not supported. The only one supported is SLL.

  • 6809: 0,X is assembled the same as ,X.

  • 6502: To enforce direct-page addressing, prepend the argument with <: <arg.