HP calcs with clock

[Katie Wasserman]

(07-16-2014 07:31 AM)x34 Wrote:  Also, I'm very confused with 28C/28S - all specs say it has no RTC, but there are lot of programs and docs using some king of internal timer. So, does 28 has any kind of internal clock/calendar ticking while calc is off?

The 28C/S has a built-in crystal controlled timer that runs continuously and can be read using a SYSEVAL call. However it does not have the firmware that converts this timer value into a date + HH MM SS, that's what those programs you found do. The built-in timer is 48 bits and clocks 8192Hz, so it's good for over 1000 years without rolling over. So yes, it does have an RTC, it's just one that reads (directly) in 1/8192's of a second.