AO Setpoint transport

The following chapters describe the operation of the PDO Value (setpoint specification for the analog output channel, Analog Output = AO).

Floating point output (Real32, default setting of the channel)

The channel expects its analog setpoint as a plain text-readable floating point value, both readable in the TwinCAT configuration

AO Setpoint transport 1:
Value (floating point value), TwinCAT

as well as in the PLC Online View:

AO Setpoint transport 2:
Value (REAL) in PLC

The Real32 PDO can simply be linked to a REAL variable in PLC:

AO Setpoint transport 3:
Linking with REAL variable

This type of transmission avoids scaling errors, as the channel itself takes into account the output range (including any range changes), commissioning and troubleshooting are considerably simplified.

Even if no unit (V, A, Ω, ..) is formally transmitted, the SI unit corresponding to the context must be used, i.e. [A] and not [mA] for a 20 mA input.

If a setpoint outside AEWtechn (output end value) is requested by the terminal, it outputs the respective maximum value and displays PDO "AO Status Overrange/Underrange + Warning":

State

Output

Setpoint > AEWtechn

"Overange" + "Warning", output AEWtechn

Setpoint < AEWtechn

"Underrange" + "Warning", output -AEWtechn

Integer output (fixed point, INT16 or SINT16)

The channel expects its setpoint as a 16-bit fixed-point value (default incl. sign, signed integer), related to AEW (output end value):

AO Setpoint transport 4:
Value (fixed-point value, "INT)"

The value range extends over -32767 ...0 ... 32768, knowledge of the output range is required for interpretation and transformation on the control side, e.g. 10V ~ x7FFF = 32767 in legacy presentation

If the channel is to be linked with existing PLC code, it can be converted to this INT16 format. Otherwise, the default setting "Real32" is recommended.

As no oversized values can be specified in INT16 format, no warning is evaluated.