User`s manual

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MELSEC-Q
8 I/O CONTROL INSTRUCTIONS
Specified position Symbol Name Recommended range
*1
Unit Data format
Standard
value
Store
D2
+124
Loop tag
past value
memory
*2 *3
+127
Used by the system as a work area. S
*1: The data of the item(s) where the values within the recommended range are given in the parentheses are stored by the system.
Users cannot set the data.
*2: The loop tag memory and loop tag past value memory occupy a total of 128 words. (Refer to Section 3.3.1 for details.)
*3: The applications of the loop tag past value memory are indicated below.
Specified position Description
D2
+124
Change rate monitor counter initial preset flag
+125 Change rate monitor counter
+126
+127
X
n-m
When control is to be started from the initial status, the data must be cleared with the sequence program.
(2) Execution cycle ( T)
Set the execution cycle in SD1500 and SD1501 as real numbers.
Processing contents
(1) Upper limit check processing
In the upper limit check processing, the following operation is performed and the result of the
operation is output to BB2 and PHA.
Condition BB2, PHA
E1 PH 1
*1
Others 0
*1: When PHI or ERRI in the alarm detection inhibition (INH) is set to 1, PHA and BB2 show 0 since the
alarm is prohibited.