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memory reserve

Download without reinitialization in TIA Portal: keeping values after an interface change

September 14, 2026 by PLC System

Instance DB of FB_Recipe drawn as three bars: 84 bytes of statics with a 100 byte memory reserve and a 100 byte retentive reserve where values stay live, the same DB after one Bool is added leaving 99 bytes of reserve with values kept, and the same change with no reserve where the DB is rebuilt from start values and the values are lost

Add one Static to an FB and every setpoint in the instance DB goes to zero. How the memory reserve prevents it, how to size it, and how to recover.

Categories PLC & HMI Tags instance db, memory reserve, recipes, S7-1200, s7-1500, tia portal

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