PLC and HMI in one, HMI is only connected to other devices through standard communication port.
In most cases, this is the case, but with the development of computer and digital circuit technology, the interface capability of human-computer interface products is constantly enhanced. In addition to the traditional external serial (RS232, RS422/RS485) communication interfaces, and some human-computer interface products have data interfaces such as Ethernet port, parallel port, USB port, and can also have a network port and industrial, parallel port
http://www.kinsealhmi.com/plc/plc-and-hmi/