Mitsubishi Electric MELSEC-Q/L Programming Manual page 105

■Device range check during indexing
• Basic model QCPU, High Performance model QCPU, Process CPU, and Redundant CPU
Device range checks are not conducted during indexing.
Therefore, when the data after index modification exceed the user specified device range, the data is read by another device
or written to another device without causing an error. (Note, however, that when the data after index modification is written to
the device for system use exceeding the user specified device range, an error occurs. (Error code: 1103))
Take extra precaution when using indexing in programming.
• QnU(D)(H)CPU, QnUDE(H)CPU, and LCPU
The device range is checked for indexing.
With changing the settings of the PLC parameter, the device range is not checked.
The timings for checking the device range during exponent modification are shown below:
Instruction
Contact instruction
Association instruction
Comparison operation instruction (LD)
Comparison operation instruction (AND)
Comparison operation instruction (OR)
Instructions other than the above
*1 When the data after index modification exceed the user specified device range, it may cause an error. (Error code: 4101).
*2 For the executions conditions for each instruction, refer to the descriptions page for each instruction.
*3 The PLS instruction and PLF instruction are excluded. (The PLS instruction and PLF instruction always check the device range during
index modification.)
Ex.
When X10Z0 exceeds the device range irrespective of ON or OFF of X0, it causes an error.
X0 X10Z0
Ex.
When D10Z0 exceeds the device range while X0 is ON, it causes an error.
The device range is not checked during index modification when X0 is OFF. Therefore, even if the D10Z0 exceeds the device
range, an error does not occur.
X0
= D10Z0
• For the QnUDVCPU:
The device range is checked during index modification.
It is also possible not to allow checking the device range using the parameters.
The timings for checking the device change during index modification are shown below.
Instruction
Contact instruction
Association instruction
Comparison operation instruction (LD)
Comparison operation instruction (AND)
Comparison operation instruction (OR)
Instructions other than the above
*4 When the data after index modification exceed the user specified device range, the operation results in OFF without causing an error.
*5 When the data after index modification exceed the user specified device range, it may cause an error. (Error code: 4101).
*6 For the executions conditions for each instruction, refer to the descriptions page for each instruction.
*7 The PLS instruction and PLF instruction are excluded. (The PLS instruction and PLF instruction always check the device range during
index modification.)
Y0
D0
Y0
Timings for checking
*1
Always
*1
When previous conditions are ON
*1
When previous conditions are OFF
It follows the execution conditions for the instruction.
Timings for checking
*4
Always
It follows the execution conditions for the instruction.
3 CONFIGURATION OF INSTRUCTIONS
3
*1*2*3
*5*6*7
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3.3 Indexing