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Increment/Decrement Instructions Section 3-10
The Equals Flag will be turned ON if the result is 0000, the Carry Flag will be
turned ON when a digit changes from 0 to F, and the Negative Flag will be
turned ON if bit 15 of Wd is ON in the result.
Both the Carry Flag and the Negative Flag will be turned ON when the content
of Wd changes from 0000 to FFFF.
Flags
Examples Operation of – –(592)
In the following example, the content of D00100 will be decremented by 1
every cycle as long as CIO 000000 is ON.
Operation of @– –(592)
The up-differentiated variation is used in the following example, so the content
of D00100 will be decremented by 1 only when CIO 000000 has gone from
OFF to ON.
Name Label Operation
Error Flag ER OFF
Equals Flag = ON if the content of Wd is 0000 after execution.
OFF in all other cases.
Carry Flag CY ON if a digit in Wd went from 0 to F during execution.
OFF in all other cases.
Negative Flag N ON if bit 15 of Wd is ON after execution.
OFF in all other cases.
D00100 D00100
−1
Decrement Decrement Decrement
Decrement
Wd: Wd:
Decremented every cycle
while CIO 000000 is ON.
: Execution of − −(592)
@− −
D00100 D00100
Decrement
Decrement
−1
Wd: Wd:
Decremented only
for up-differentiation.
: Execution of @− −(592)
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