1. In a programmable sequence controller (PC) for controlling a machine, including means for receiving status data from said machine, a program memory for storing a set of program instructions for controlling the machine, and means for generating a control signal for controlling the machine responsive to the program instructions set and said machine status data, and where said PC may be linked via a common data bus to other PCs which control other machines, the improvement comprising: data transfer means for transmitting said machine status data to said common data bus, and for receiving from said common data bus, the status bus of the machines associated with said PCs; and input/output (I/O) status memory means for storing said machine status data and said other status data, thereby providing said PC with the ability to generate a control signal that can be responsive to said other data , said I/O status memory means including an I/O memory for storing said machine and said other status data, and a flag memory for marking an address of said I/O memory to indicate the presence or absence of a communication occurring between any of said PCs and its associated machines.