RTC(HW) UNIX System V
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 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 register 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.
Files
/dev/rtc
(printed 8/30/89) RTC(HW)