Previously, PLCs were designed with proprietary ASICs (application-specific integrated circuits) and general-purpose embedded processors used to control and monitor the system. The ASIC running the user program determined the core processing performance and functionality of the PLC. A drawback to this approach is custom ASICs are expensive to develop and manufacture, particularly with the higher costs associated with the latest semiconductor process technologies. The production of ASICs requires unique and costly photomasks, which are amortized over a relatively small PLC volume, making the cost per chip very high compared to ASICs used in mass-produced household appliances. Another issue is lead-time, since ASIC development can take as long as two years, followed by more time needed to test and qualify the operation of the ASIC as part of the PLC system.

OMRON's new NJ501 integrated machine controller is based on Intel architecture. See the whole case study from the Intel web site to  find out why.