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3.27 Memory Check Function
This function checks whether data in the memories of the CPU module are not changed due to such as excessive
electric noise.
Since the CPU module automatically checks a memory, setting for enabling this function is unnecessary.
This function does not require processing time.
(1) Data to be checked
(a) Program
The program during execution is compared with the user program written to the program memory.
If they do not match, a stop error, "RAM ERROR" (error code: 1160) is detected.
(b) Parameter
The parameters are compared with the ones written to the parameter-valid drive.
(c) Device memory
If the CPU module detects the change of data in the device memory, a stop error, "RAM ERROR" (error code:
1161) occurs. For the Universal model QCPU whose serial number (first five digits) is "13022" or later, the
device information, which contains data change information, can be checked in SD927 and SD928. For details
on the special register, refer to the following.
QCPU User's Manual (Hardware Design, Maintenance and Inspection)
(2) Execution timing
• Program: At program execution
• Parameter:
• Device memory: When device data are read
• When the CPU module is powered off and then on
• When the CPU module is reset
• When the CPU module is set from STOP to RUN after data are written to it
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