The RTC IC has a low voltage detector which sets a bit in the seconds register. Thus (from the IC data sheet):
8.5 Voltage-low detector and clock monitor The PCF8563 has an on-chip voltage-low detector. When VDD drops below Vlow the VL bit (Voltage Low, bit 7 in the Seconds register) is set to indicate that reliable clock/calendar information is no longer guaranteed. The VL flag can only be cleared by software So it's easy, just software ;-) Richard KL0DR At 10:43 AM 6/24/2010, Brian Alsop wrote: >David Ferrington, M0XDF wrote: > > Regarding the battery, is there a way to check it's voltage or > projected life - without taking the cover off and measuring it? > > 73 de M0XDF > >Reminds me of the same suggestion implemented in a few IBM prototype >PC'S for the CMOS battery. They devised a circuit to go in and test it >many times per day. Unfortunately, the act of repeatedly testing it >removed enough energy to greatly shorten battery life. > >They dropped the idea. > >73 de Brian/K3KO >______________________________________________________________ >Elecraft mailing list >Home: http://mailman.qth.net/mailman/listinfo/elecraft >Help: http://mailman.qth.net/mmfaq.htm >Post: mailto:Elecraft@mailman.qth.net > >This list hosted by: http://www.qsl.net >Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
