TS-7600 RTC

From Technologic Systems Manuals

This board includes a temperature compensating RTC which maintains ±5 ppm between 0C to +85C. This is accessed in software using tshwctl. By default, tshwctl will run "tshwctl --getrtc" on startup which will pull system time from the RTC, and set the system time. During the Technologic Systems production process the RTC will be programmed with an accurate time.

If time ever needs to be set you can run:

tshwctl --setrtc

This will take the system time and write it to the RTC. The battery in the RTC will last approximately 10 years for most applications, but the RTC allows you to see when the battery reaches low or critical voltages:

# tshwctl --rtcinfo             
rtc_present=1                   
rtctemp_millicelsius=36000      
rtcinfo_oscillator_ok=1         
rtcinfo_batt_low=0         
rtcinfo_batt_crit=0         
rtcinfo_firstpoweroff=0000000000
rtcinfo_lastpoweron=0000000000

rtcinfo_oscillator_ok is true when the RTC is operational and time is being kept
rtcinfo_batt_low is true when the battery is less than 2.805v (85% of 3.3v)
rtcinfo_batt_crit is true when the battery is less than 2.475v (75% of 3.3v)

Note: While the RTC will remain operational with a battery voltage down to 1.8v, the lithium battery used has a very steep discharge curve. Once the battery reaches critical level it should be replaced.


rtcinfo_first/lastpoweroff/on are two registers that denote the first time the RTC started using battery power, and the last time power was restored and the RTC stopped using battery power for timekeeping. The output of these registers is in the format MMDDhhmmss. Once `tshwctl --rtcinfo` is called, these registers are cleared and able to be set again. This is a great tool to check if a power off has occurred and how long it lasted.