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Increment/Decrement Instructions Section 3-9
Description The – –L(593) instruction subtracts 1 from the 8-digit hexadecimal content of
Wd+1 and Wd. The content of the specified words will be decremented by 1
every cycle as long as the execution condition of – –L(593) is ON. When the
up-differentiated variation of this instruction (@– –L(593)) is used, the content
of the specified words 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 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+1 is ON in the result.
Both the Carry Flag and the Negative Flag will be turned ON when the content
changes from 0000 0000 to FFFF FFFF.
Flags
Examples Operation of – –L(593)
In the following example, the 8-digit hexadecimal content of D201 and D200
will be decremented by 1 every cycle as long as CIO 0.01 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+1 Wd Wd+1 Wd
Name Label Operation
Error Flag ER OFF
Equals Flag = ON if the result is 0000 0000 after execution.
OFF in all other cases.
Carry Flag CY ON if a digit in Wd+1 or Wd went from 0 to F during exe-
cution.
OFF in all other cases.
Negative Flag N ON if bit 15 of Wd+1 is ON after execution.
OFF in all other cases.
D201 D200 D201 D200
−1
0.01
0.01
D200
Decrement Decrement DecrementDecrement
Wd+1: Wd: Wd+1: Wd:
Decremented every cycle
while CIO 0.01 is ON.
: Execution of − −L(593)
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