The invention relates to the technical field of communication cascading, and discloses a
visual detection signal input and output multi-
machine communication cascading technology. According to the invention, two TTL-to-RS422 level conversion chips are used, a pin 1 and a pin 4 of a U9 are used for supplying power, a pin 5, a pin 6, a pin 7 and a pin 8 of the U9 are connected with an upper level, and a pin 2 and a pin 3 of the U9 are connected with a
serial port 1 of an MCU (Microprogrammed
Control Unit) singlechip, namely upper-level equipment in a
software program. A pin 1 and a pin 4 of a U17 supply power, a pin 5, a pin 6, a pin 7 and a pin 8 are connected with the next level, and a pin 2 and a pin 3 are connected with a
serial port 3 of the MCU singlechip, namely next-level equipment in the
software program. According to the invention, the input and output
signal controller is expanded hierarchically, so that the
signal control box can be expanded according to the demand when the customer demand is increased; the problem that a slave cannot initiate communication to a host actively is solved from the perspective of hardware; the slave can actively initiate communication to the host at any time. The expansion problem of the input and output signal controller and the problem that instant response cannot be achieved in master-slave communication are solved.