tst

Test

Sets the condition codes from the operand, as if comparing it with zero.

Sizes .b .w .l, .w by default

Used in

The condition code registerM68K assembly
Compare and branchM68K assembly
Loops and dbraM68K assembly
Arithmetic, logic and bitsM68K assembly
Arrays, strings and (a0)+M68K assembly
Exceptions and the vector tableM68K assembly
Length of a stringM68K assembly
Reverse a string in placeM68K assembly
A subroutine with its arguments in registersM68K assembly
Move a square with the keyboardM68K assembly

XNZVC –●●00

● set from the result
0 always 0
– not changed

Forms

tst

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

* --- Testing different values ---
move.l #$80, d0
tst.b d0 ; N flag set (bit 7 = 1)

move.l #$00, d1
tst.b d1 ; Z flag set

move.l #$7F, d2
tst.b d2 ; no flags (positive, nonzero)1
2
3
4
5
6
7
8
9