rtc(HW) 19 June 1992 rtc(HW) Name rtc - real time clock interface Description The rtc driver supports the real time clock chip, allowing it to be set with the correct local time and allowing the time to be read from the chip. ioctl calls RTCRTIME This call is used to read the local time from the real time clock chip. The argument to the ioctl(S) is the address of a buffer of RTCNREG unsigned characters (RTCNREG is defined as <sys/rtc.h>). The ioctl will fill in the buffer with the contents of the chip registers. Currently, RTCNREG is 14, and the meanings of the byte registers are as follows: ____________________________________________________ Register Contents ____________________________________________________ 0 Seconds 1 Second alarm 2 Minutes 3 Minute alarm 4 Hours 5 Hour alarm 6 Day of week 7 Date of month 8 Month 9 Year A Status register A B Status register B C Status register C D Status register D For further information on the functions of these registers, see your hardware technical reference manual. RTCSTIME This call is used to set the time into the real time clock chip. The argument to the ioctl is the address of a buffer of RTCNREGP unsigned characters (RTCNREGP as defined in <sys/rtc.h>). These bytes should be the desired chip regis- ter contents. Currently, RTCNREGP is 10, representing registers 0-9 as shown above. Note that only the super user may open the real time clock device for writing and that the RTCSTIME ioctl will fail for any other than the super user. File /dev/rtc