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Increment/Decrement Instructions Section 3-9
Description The – –B(596) instruction subtracts 1 from the BCD content of Wd. The spec-
ified word will be decremented by 1 every cycle as long as the execution con-
dition of – –B(596) is ON. When the up-differentiated variation of this
instruction (@– –B(596)) is used, the specified word is decremented only
when the execution condition has gone from OFF to ON.
The Equals Flag will be turned ON if the result is 0000 and the Carry Flag will
be turned ON when a digit changes from 0 to 9.
Flags
Precautions The content of Wd must be BCD. If it is not BCD, an error will occur and the
Error Flag will be turned ON.
Examples Operation of – –B(596)
In the following example, the BCD content of D1000 will be decremented by 1
every cycle as long as CIO 0.00 is ON.
Index Registers ---
Indirect addressing
using Index Registers
,IR0 to ,IR15
–2048 to +2047, IR0 to –2048 to +2047, IR15
DR0 to DR15, IR0 to IR15
,IR0+(++) to ,IR15+(++)
,–(– –)IR0 to, –(– –)IR15
Area Wd
−1
Wd Wd
Name Label Operation
Error Flag ER ON if the content of Wd is not BCD.
OFF in all other cases.
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 9 during execution.
OFF in all other cases.
D1000 D1000
−1
0.00
D1000
CIO 0.00
Decrement Decrement Decrement Decrement
Wd: Wd:
Decremented every cycle
while CIO 0.00 is ON.
: Execution of − − B(596)
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