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suba

Subtract address

Subtracts the first operand from an address register, sign extending a word to long and leaving sr unchanged.

Sizes .w .l, .w by default

XNZVC –––––
  • Changes no flag

Forms

Operands

<ea>
An operand using one of the instruction’s supported addressing modes, such as d0, (a0)+ or 4(a1). It may name a register, memory or an immediate value. More
An
An address register, a0 to a7; sp is another name for a7. More
#imm
An immediate value written after #: a number, character or label, such as #10, #$FF or #'a'. It must fit the operation’s size: byte -128 to 255, word -32768 to 65535, or long -2147483648 to 4294967295; signed and unsigned spellings are accepted. More

It does not change the SR. When using word size, the first operand is sign extended to long and the second is read and written as a long.

* --- Word is sign-extended before subtracting ---
move.l #$10000, a0
suba.w #$0002, a0

* --- Does NOT affect flags ---
move.l #0, d0
tst d0
suba.l #$FFFFF, a1 ; flags unchanged (Z still set)