NOVRAM
CX20x3
52
Version: 1.0
8
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.
Fig. 25: Controller behavior with and without NOVRAM.
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 environ-
ment
Target platforms
Hardware
PLC libraries
to include
TwinCAT 3.1 Build: 4020
PC or CX (x86, x64, ARM) CX9020, CX20x0,
CX20x2, CX20x3
Tc2_IoFunctions
