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Section
07 Part 01 The SEQ, SNE, SPL & SMI Instructions |
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Self-esteem is the greatest sickness known to man or woman
because it's conditional." ~Albert Ellis |
Introduction
The S##
instructions coming up are pretty much the same as conditional branches, they perform an action based on the same sort of
conditions. The difference however, is
that instead of branching, these instructions set or clear bits on the destination operand.
The SEQ Instruction
SEQ Set on EQual
The Z (Zero) flag is tested, if true, the
destination
operand is set (%11111111), if false, the destination operand is cleared (%00000000).
Example
This
is rather simple:
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tst.l d0 seq.b d1 |
The TST
instruction will check d0
for zero, it's a long-word check.
It couldn't be simpler.
The SNE Instruction
SNE Set on Not Equal
The Z (Zero) flag is tested, if true, the
destination
operand is
cleared (%00000000), if false, the destination operand is set (%11111111).
Example
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tst.l d0 sne.b d1 |
The TST
instruction will check d0
for zero, it's a long-word check.
It is pretty much the opposite of SEQ.
The SPL Instruction
SPL Set on PLus
The N (Negative) flag is tested, if true, the
destination
operand is
cleared (%00000000), if false, the destination operand is set (%11111111).
Example
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tst.b d0 spl.b d1 |
The
TST instruction will check d0
for positive/negative, it's a byte check.
ท
If d0 was
between 80 and FF
(Negative), the N
flag would be set. The SPL instruction
will set d1 as 00000000.
The SMI Instruction
SMI Set on MInus
The N (Negative) flag is tested, if true, the
destination
operand is set (%11111111), if false, the destination operand is cleared (%00000000).
Example
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tst.b d0 smi.b d1 |
The
TST instruction will check d0
for positive/negative, it's a byte check.
It is the opposite of SPL.