Sequence control system

A sequence controller for effecting sequence control of a process to be controlled by sequentially accessing and reading a selected one of a plurality of sequence programs, said sequence controller comprising:

• a sequence program memory for storing a plurality of sequence programs;
• a process I/O unit including a scanner and switching means, said scanner including means for sequentially inputting signals indicative of conditions of the process to be controlled through said switching means and for sequentially applying control signals to the process to be controlled through said switching means;
• a buffer memory including an input memory portion for storing the signals indicative of the conditions of the process which are sequentially inputted from the process to be controlled through said process I/O unit, and an output memory portion for storing the control signals for the process which are sequentially obtained in accordance with a sequence program read out of said sequence program memory;
• means for selectively connecting said buffer memory to said switching means in said process I/O unit for transmitting the signals indicative of the conditions of the process and the control signals for the process therebetween;
• a sequence processing unit connected to said sequence program memory and said buffer memory for processing a sequence program selectively read out of said sequence program memory on the basis of data stored in said input memory portion of said buffer memory and applying results of the processing operation to said output memory portion as the control signals for the process;
• setting means for manually selecting a sequence program in accordance with a sequence logic of the process to be controlled and for manually setting conditions of the process to be controlled, said setting means including means for outputting a first signal indicative of a selected sequence program and a second signal indicative of set conditions of the process;
• control means connected to said setting means and coupled to said sequence program memory for selectively reading a corresponding sequence program from said sequence program memory in accordance with said first signal and for applying the selected sequence program to said sequence processing unit, and having means for setting the conditions of the process in said input memory portion in accordance with said second signal;
• and
• display means for selectively displaying conditions of a sequence program stored in said input and output memory portions of said buffer memory;
• whereby, when the conditions of the process are sequentially applied to said input memory portion and the control signals for the process are applied from said output memory portion to the process through said process I/O unit and said connecting means in response to said control means, said display means displays operating conditions of a sequence program selected by said setting means in accordance with the conditions of the process set in said input memory portion through said process I/O unit, and when said connecting means disconnects said process I/O unit from said buffer memory, said display means displays operating conditions of a sequence program selected by said setting means in accordance with the signals indicative of conditions of the process which are set by said setting means and stored in said input memory portion.