PLC18V8Z APPLICATIONSThe 80C51 microcontroller and its CMOSderivatives have two power reducing modes,Idle and Power Down. The Power Downmode reduces the device’s current to lessthan 50µA by only keeping the on-chip RAMand SFRs data intact. In order to resumeoperation while in the Power Down mode, it isnecessary to apply a reset to themicrocontroller.The PLC18V8Z is in a low power modewhenever its inputs are not switching,drawing less than 100µA. An input transitioncauses the PLC18V8Z to power up itsinternal array for a short time, latch a validoutput and then return to low power mode.Because of this transparent power reductionfeature and its programmability, thePLC18V8Z is an excellent device to use inlow power applications with an 80C51microcontroller.Two examples of using the PLC18V8Z with aSC87C751 microcontroller are presented.Both applications use the PLC18V8Z todetect events while the SC87C751 is in aPower Down mode and then reset (wake up)the microcontroller. The first exampl...