NOVRAM
The NOVRAM can be used to reliably save important variable values, such as production data or counter values, in the event of a power failure. The memory size of the NOVRAM is limited and only suitable for smaller data quantities up to 63 kB.
In this chapter we show you how the NOVRAM is used in TwinCAT 3.
Functioning
The NOVRAM (Non-Volatile Random Access Memory) is a special memory component that is used to reliably save important data. The NOVRAM consists of two sections, a volatile memory and a non-volatile memory.
TwinCAT only writes to the volatile section of the NOVRAM. In the event of a power failure, the data are automatically copied from the volatile memory into the non-volatile memory. The energy required for this process is supplied by a capacitor. As soon as the power supply is restored, the data are automatically copied back into the volatile memory, so that TwinCAT can continue to use them.
Memory size
The NOVRAM has a capacity of 128 kB. However, for reasons of data consistency, effectively less than 63 kB of data can be securely saved in the NOVRAM. The data are saved cyclically and alternately based on the dual buffer principle, in order to avoid the risk of data inconsistency.
Requirements
Development environment | Target platforms | Hardware | PLC libraries |
|---|---|---|---|
TwinCAT 3.1 Build: 4020 | PC or CX (x86, x64, ARM) | CX70xx, CX9020, CX20x0, CX20x2, CX20x3 | Tc2_IoFunctions |