A programmable controller includes a CPU unit, a communication unit and peripheral units connected together through an internal bus. The communication unit has a bus master function, including a cache memory for recording IO data stored in the memory of an input-output unit. When a message is received,...http://www.google.com.au/patents/US7509440?utm_source=gb-gplus-sharePatent US7509440 - Programmable controller and communication unit therefor
