When designing a complex machine, engineers have two options. They can get all parts of the system—controller, drives, motors, I/O and human-machine interface (HMI)—from a single vendor. Or, they can pick and choose devices from multiple suppliers.
Each strategy has benefits and limitations. The former has the benefit of convenience. Setting up peripheral devices, like the I/O and HMI, is easier within a common platform. On the other hand, the supplier may not offer a complete range of peripherals.