Multiple PLC channels can exists in a single PLC card, regardless of whether these are digital or analog input or output modules. PLC modules with 8, 16, or 32 channels are often used. Every PLC channel is assigned a unique address.
In addition to a signal connection point, a channel can also consist of multiple associated PLC connection points. The PLC cards of some manufacturers have additional power supply connection points for every channel. This allows (e.g.) a 3 conductor proximity switch to be directly connected to a PLC card. In this case, two PLC connection points provide the required operating voltage for the sensor and the third PLC connection point receives the sensor signal.
If inputs or outputs with power supply connection points are planned in EPLAN, the channel assignment is done graphically or via the channel designation.
All data that is important in assignment lists is also relevant to a channel, e.g. the symbolic address or the function text. This data is stored or determined at the PLC connection point with the "DI=Digital input", "AI=Analog input", "DO=Digital output" or "AO=Analog output" function definition.
Channels with several I/O connection points
A channel can have several I/O connection points, but only one of them can be active. All the other I/O connection points within the channel must be marked as disabled, by assigning them the property Deactivated I/O connection point. This means that the same macro and the same part can be used for different wiring configurations.
Example:A macro contains an analog channel with two I/O connection points to which the Deactivated I/O connection point property is assigned. You can use this macro with different wirings for measuring current or voltage. Once the macro has been added, activate the I/O connection point that matches the wiring by deactivating the Deactivated I/O connection point property there.
Deactivated connection points are treated as power supplies. For example, when addressing a filled address, the address from the channel is overwritten.
Safety controllers
PLC cards that can check multiple connection points each for equality and difference are often used for safety controllers. At such safety-relevant characteristics PLC configuration programs often manage multiple channels with the same symbolic address. Since the symbolic address within the CPU must be unique, only one I/O connection point may be active within a channel. Therefore designate the other connection points with the property Deactivated I/O connection point. This way these connection points are not filled with data inaccurate for the PLC configuration program during the PLC data exchange.
To allow the post-addressing of these connection points in EPLAN, enter the same value in the Channel designation field for each of the combined connection points.
See also