Digital input modules feature the following mechanical characteristics:
Compact design: The rugged plastic housing contains:
Green LEDs for indicating the signal status at the inputs.
Socket for the front connector, protected, behind the front door.
Labeling field on the front door.
Connector pin assignment for the wiring on the inside of the front door.
Easy installation: There are no slot rules, the addresses of the inputs are determined by the slot. When used in ET 200M in combination with active bus modules, hot swapping is possible without any reaction.
The modules are available with 8, 16, 32, or 64 channels.
Digital input modules convert the level of the external digital signals from the process to the internal signal level (logical “0” or “1”) of the controller.
Various input voltages support the connection of different process signals:
24 V DC
48 to 125 V DC
120/230 V AC
Apart from cost-effective, easy-to-handle modules, modules with special functions are also available:
For use in isochronous mode
Process and diagnostic alarms
Use for current sourcing or current sinking
Special modules are also available for process engineering which, for example, support the NAMUR standard.
Product No. / Product Description
SM 321 digital input modules Ordering data
SIMATIC S7-300, DIGITAL INPUT SM 321, OPTICALLY ISOLATED, 16DI, 24 V DC, 1 X 20 PIN