|nOffset||(Long) Specifies the position of read value in the data block.
The read value must be inside the data block. The item is read either whole or not read at all.
>= 0 - Index (in bytes, zero-based index) in the data block.
-4 - The internal automatic position is used (see the AutoOffset property). It points behind the last read or written value.
This operation shifts the internal automatic position behind the read/written value.
If the items are read/written one by one then it is not necessary to define the position manually, but it is better to use this automated positioning.
|nEncoding||[optional] (Long) Byte saving order in the memory of a single value (Little-endian/Big-endian) in the data block. The Little-endian and Big-endian use different (reversed) order of the value bytes storage in memory. This is not depending on the operating systerm but on the computer platform.
In the PROMOTIC system (on x86 computer CPUs) the Little-endian is used.
Big-endian is commonly used on ARM processors (usually used for communication with PLC devices). Big-endian may be required for data exchange with another system (e.g. PLC device).
var oBuf = Pm.CreatePmBuffer();
var val0 = oBuf.GetFloat64(0);
var val1 = oBuf.GetFloat64(8);
oBuf.AutoOffset = 0;
var val0 = oBuf.GetFloat64(-4);
var val1 = oBuf.GetFloat64(-4);