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Increment/Decrement Instructions Section 3-9
Description The – –(592) instruction subtracts 1 from the binary content of Wd. The spec-
ified word will be decremented by 1 every cycle as long as the execution con-
dition of – –(592) is ON. When the up-differentiated variation of this instruction
(@– –(592)) is used, the specified word is decremented only when the execu-
tion condition has gone from OFF to ON.
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 D100 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
Wd
Wd
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.
D100 D100
−1
0.00
CIO 0.00
D100
Decrement Decrement Decrement Decrement
Wd: Wd:
Decremented every cycle
while CIO 0.00 is ON.
: Execution of − −(592)
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