HostLink[1] is Omron's protocol for communication over serial links. It is an ASCII-based protocol generally used for communication over RS232 or RS422.The maximum message size allowed is 30 words per message. Larger messages can be sent by 'fragmentation' process, where the same slave returns a series of messages to build up the entire response. PLC host computer can transfer procedures, and monitor PLC data area, and the control PLC using HostLink protocol.