MITSUBISHI ELECTRIC Mitsubishi Programmable Logic Controller QD75D - Manual (Page 579)

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MELSEC-Q
13 COMMON FUNCTIONS
13.3 Execution data backup function
When the QD75 buffer memory data is rewritten from the PLC CPU, "the data backed
up in the QD75 flash ROM" may differ from "the data (buffer memory data) for which
control is being executed".
In cases like these, the data being executed will be lost when the PLC power is turned
OFF. (Refer to Chapter 7.)
In cases like these, the "execution data backup function" backs up the data being
executed by writing it to the flash ROM. The data that was backed up is then written to
the buffer memory when the power is turned ON next.
The details shown below explain about the "execution data backup function".
[1] Execution data backup means
[2] Control details
[3] Precautions during control
[4] Execution data backup method
[1] Execution data backup (written to flash ROM) means
• The backup is executed with a sequence program.
• The backup is executed by peripheral device.
Refer to GX Configurator-QP Operating Manual for execution data backup
method by peripheral device.
[2] Control details
The following shows the data that can be written to the flash ROM using the
"execution data backup function".
Buffer memory Flash ROM
Parameters ( Pr.1 to Pr.57 , Pr.150 ) Parameters ( Pr.1 to Pr.57 , Pr.150 )
Positioning data (No. 1 to No. 600) Positioning data (No. 1 to No. 600)
Block start data (No. 7000 to 7004) Block start data (No. 7000 to 7004)
[3] Precautions during control
(1) Data can only be written to the flash ROM when the positioning control is not
carried out (when the PLC READY signal (Y0) is OFF).
(2) Writing to the flash ROM can be executed up to 100,000 times.
If writing to the flash ROM exceeds 100,000 times, the writing may become
impossible, and a "flash ROM write error (error code: 801)" will occur.
(3) After one power ON/PLC CPU reset operation, writing to the flash ROM
using a sequence program is limited to up to 25 times.
If the 26th writing is executed, a "flash ROM write number error (error code:
805)" will occur. If this error occurs, carry out the power OFF ON/PLC
CPU reset operation again.
Refer to Md.19 of Section 5.1.7 "Types and roles of monitor data" for
details.
Important
Do not turn the power ON/OFF, reset the PLC CPU, during writing to the flash
ROM. The flash ROM data may be corrupted.