pic 12ce518 device which contains 512 words of program rom implemented as otp eprom and includes a 16 by 16 eeprom the specifications of the preferred components of the water filter status monitoring and indicating system 70 are as indicated on table 1 on fig4 b programming logic of the water filter status monitoring and indicating system fig5 through fig8 illustrate the programming and logic of the water filter status monitoring and indicating system 70 which is programmed into the microprocessor device 140 the logic is intended to provide programming for alternative models such as an a model refrigerator a b model refrigerator or a c model refrigerator each having different functionality the various models may have different replacement criteria for the filters depending on the gallon rating and the useful life of the filter referring to fig5 when the power is first supplied to the microprocessor device 140 a power up subroutine 200 is initiated at step 202 the microprocessor device reads the stored memory at step 204 the microprocessor device 140 sends a signal to the indicator 66 to flash red if the refrigerator is a model a and green if it is a model b the microprocessor device 140 then enters a continuously repeated main subroutine 206 within each repetition of main subroutine 206 microprocessor device 140 updates its clock at step 208 and once every 18 hours stores the time and water used in the non volatile memory at step 210 at steps 212 and 214 respectively the amount of water used is incremented if the ice valve 52 is open or if the fresh water valve 54 is open the open time for each valve 52 and 54 is weighted for the normal water flow rate associated with the valve at.