System and method for synchronizing messages using a least common multiple in industrial process control and automation systems

An apparatus comprising:

• at least one network interface configured to communicatively connect to at least one expansion controller that controls a plurality of input/output (I/O) modules;
• and
• at least one processing device configured to:
• determine a scan rate associated with each of the I/O modules;
• transmit a read request message to the at least one expansion controller, the read request message having an align index field;
• receive a reply message from the at least one expansion controller for each of the I/O modules for which a value of the align index field of the read request message is an even multiple of the associated scan rate;
• increment the value of the align index field;
• and
• repeat the transmitting, receiving, and incrementing until the value of the align index field is greater than a threshold, wherein the threshold is a least common multiple of the scan rates of the plurality of I/O modules.

A non-transitory computer readable medium containing instructions that, when executed by at least one processing device, cause the at least one processing device to:

• determine a scan rate associated with each of a plurality of input/output (I/O) modules;
• transmit a read request message to at least one expansion controller that controls the plurality of I/O modules, the read request message having an align index field;
• receive a reply message from the at least one expansion controller for each of the I/O modules for which a value of the align index field of the read request message is an even multiple of the associated scan rate;
• increment the value of the align index field;
• and
• repeat the transmitting, receiving, and incrementing until the value of the align index field is greater than a threshold, wherein the threshold is a least common multiple of the scan rates of the plurality of I/O modules.