Programmable controller and communication interface therefor

A communication interface as a part of a programmable controller, serving to carry out command-response communications with an external general-purpose device connected through a specified communication line according to a preliminarily stored program, said communication interface comprising:

• relaying means for converting a command addressed to said external general-purpose device and received from a peripheral device through said programmable controller so as to become suitable for communication through said specified communication line, converting a response from said external general-purpose device corresponding to said received command into a response to said peripheral device and relaying said converted response to said programmable controller;
• processing means for transmitting said received command to said external general-purpose device and receiving said response from said external general-purpose device corresponding to said transmitted command;
• and
• control means for judging whether or not said processing means is in a wait condition for said response when said command addressed to said external general-purpose device is received, causing said converted command to be transmitted to said external general-purpose device through said processing means if said processing means is judged not to be in said wait condition, not transmitting said converted command if said processing means is judged to be in said wait condition, and making communications with said external general-purpose device through said processing means when said wait condition ends.

A network system comprising:

• a programmable controller having a communication interface mounted thereto;
• a peripheral device connected to said programmable controller;
• and
• an external general-purpose general purpose device connected to said communication device;
• said communication interface judging whether or not said communication interface is in a wait condition for a response from said external general-purpose device when a communication command issued by said peripheral device addressed to said external general-purpose device is being relayed, temporarily stopping the relay in said wait condition and carrying out a communication with said external general-purpose device when said wait condition ends.

A programmable controller comprising:

• program executing means for executing a user program for controlling a control device;
• and
• a communication interface serving to carry out command-response communications with an external general-purpose device connected to said programmable controller through a specified communication line according to an execution command from said user program, said communication interface comprising:
• relaying means for converting a command addressed to said external general-purpose device and received from a peripheral device through said programmable controller so as to become suitable for communication through said specified communication line, converting a response from said external general-purpose device corresponding to said received command into a response to said peripheral device and relaying said converted response to said programmable controller;
• processing means for transmitting said received command to said external general-purpose device and receiving said response from said external general-purpose device corresponding to said transmitted command;
• and
• control means for judging whether or not said processing means is in a wait condition for said response when said command addressed to said external general-purpose device is received, causing said converted command to be transmitted to said external general-purpose device through said processing means if said processing means is judged not to be in said wait condition, not transmitting said converted command if said processing means is judged to be in said wait condition, and making communications with said external general-purpose device through said processing means when said wait condition ends.