In the world of PCs, COM ports have long been replaced by USB.

However, in the area of industrial communication between devices,

serial interfaces are still highly relevant. Even an RS-232 connection

permits longer cable distances than USB. The balanced signal transmission

of RS-422 enables robust data exchange over several kilometers – and

this with a cost-effective copper cable. The RS-485 standard is suitable

for both point-to-point connections and bus topologies with up to 32

participants.

A wide range of communication partners are available. Interoperability

is ensured by standards such as IEC 60870-5-101. -103 or DNP3 Serial.

Even proprietary protocols for peripheral devices, such as connecting an

RFID reader, can usually be quickly integrated into an application program.

As well as performance, security is a key driver for the choice of COM-ports

as serial interfaces. The point-to-point connection via physical cable

between clearly identifiable devices offers a high level of security, as the

communication cannot be disrupted by intermediate devices or network

components. Cyberattacks on devices connected via COM ports are harder

to execute and usually easier to detect compared to those in a TCP/IP network.