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FX1S data retention time limit

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Is there a time limit to how long data can be stored in the latched registers of an FX1S (D128-255) until it is lost if the power is off for an extended period of time?

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Right in the FX1S Hardware Manual, section 1.5 JY992D83901 --- Data includes the Program, Comment, File Register (D1000 ~ D2499), and parameter data. This will be stored as long as the EEPROM is not damaged. Mitsubishi Electric has guaranteed a life cycle time of 10,000 writes to the EEPROM memory. Users may experience operational writes to the EEPROM in excess of 10,000; however, due to temperature effects a quantitative estimation cannot be given. If the PLC has been powered ON for five minutes or more, the following device data will be saved in the EEPROM at power-down: S0~S127, M384 ~ M511, C16 ~ C31, C235 ~ C255 and D128 ~ D255. If the PLC is powered ON for less than 5 minutes, the above data is not saved!

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Haven't read the manual right now, but I'm pretty sure that all the devices are NOT stored in EEPROM at shudown. They are stored in a RAM which is powered by a capacitor, hence the time powered off will rely on the capacitor which is guaranteed 3 days, but personally I would say ebout 10-12 days. Program, comments and parameter data are indeed saved in an EEPROM but NOT the content of all the registers, timers, counters +++ Another thing to be aware of is that when powered of for a longer period of time than the capacitor handles, the data in the devices are NOT set to zero or 0xFFFF. They are completely inconsistend so you MUST use initialization tasks to ensure that there are no corrupt data. Correct me if I'm wrong.

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You are not right, Kaare. The schematic of FX1S is another than FX2N, where the current data of retentive devices are stored in RAM, powered by ionistor. We used FX1S as tester to check a communication with another equipment, that is manufactured from time to time. I.e. the tester is used rarely, the link test occupies several minutes and 99.9% of time the tester is powered off. It stores a set of predefined datagrams for sending and during several years we never lost data. Edited by Inntele

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What do you mean by datagrams?? Are they pre-defined like you've hard-typed them to move into registers, or are they like a recipe where values are stored in e.g. D0-D100?? Program, comments and parameters are stored indeed, and both the FX1S and FX1N uses an EEPROM for this, my worry is the data inside the dataregisters. I've personally experienced this in an FX1N and I thought that the FX1S was the same... Just to clearify: All program, comments, parameters, and any "hardcoded" values are indeed stored in EEPROM, but the values inside the dataregisters are not stored in EEPROM... Also; how do they solve saving xxx number of dataregisters, timer-values, counter-values and so on right before the PLC shuts down?? Is there a sensor and a capacitor that are triggered when detecting a power off, and then writes all the dataregisters to the EEPROM?? It's impossible to continously write all the dataregister to the EEPROM since it has a 10.000 limit for writing which is/was common for EEPROM's. As said, the FX1N works the way I'm saying (everything is stored EXCEPT any dynamic value inside the D-registers ++), so correct me if the FX1S is different...

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Dear Kaare, the datagrams are stored as a set of pre-defined values in the retentive data registers (from D128 to D255). The data never were lost during several years. In contrast to FX2N, we've not delved inside FX1S and FX1N therefore can't say is it provided with EEPROM, as written in manual, or by other schematic. Can state the fact only.

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@Inntele: Yes, you are correct. Just checked the manual (see attached picture) and some devices are indeed backed up automatically by the EEPROM!!! The FX1S obviously has a different function than FX1N!

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That's the part of the manual which I had copied into my original reply. That's why I found it odd you were disagreeing kaare_t!

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This topic has highlighted one important issue: the developer has not a clear understanding of where his programs, parameters and data table will be recorded, stored as a copy and for running, what processes are happening directly after the PLC has been powered on or off. The developer does not have a clear idea what will happen with the program and data in PLC at failure of nutrition of the memory chip or its checksum. When I worked with Siemens S7-200 series, all these issues has been thoroughly described in the documentation. While Mitsubishi is silent, limited only meager sentences, and thus leaving the field for imagination and subjective conclusions that are often very far from reality.

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