Siemens S7-224 EEPROM (retentive ?)

[Tom001]

If I were to fit an EEPROM to a S7 plc, how can i make my program extract vwords from the eeprom and write them to it? All i want to do is recall/write values set on a TD200 but will this actually achieve anything or is there another way of making the PLC retain the contents of certain vwords.

Thanks

Tom

 

[jonesy29847]

Does your PLC support EEPROM? I think you need to supply a programming voltage to the chip to write to it. This would seem to be very difficult as you would have to modify the circuit board, or is there something I'm not seeing here.

There may be other ways to make the PLC memory retentive, some processors require you to set them up for retentive memory.

Are you doing this so you can restore contents after changing the processor, or do you loose data on power down.

 

[Kiljoy]

Check the system manual for your PLC. We currently use the S7-226. As long as the power is not lost for more than a couple of days, the V-words set to be retentive will stay put (internal back-up capacitor). Using the MicroWin software, one can set which memory ranges are retentive via the system block. Adding the optional battery cartridge will extent the retentive memory to around 200 days.
As for the EEPROM; if it is installed, it will load every power cycle. We burn the program to the EEPROM (for backup) and then replace it with the battery so our user values don't change every time someone turns the machine off for the weekend.
The only way I know to write to the EEPROM is being online with the PLC via the MicroWin software.

 

[Tom001]

Thanks Guys,

All I wanted to do was retain certain default timer values that are held in VWORDS that are normally adjusted on a TD200 but i had to put an option for entering default values automatically as someone is bound to fiddle and I have used around 40 timers.

Set the retentive range in the system block worked, also fitted the battery module, now retining the data i required.

Thanks KilJoy

Regards,

Tom