ref: bbd6a23c4f306339b4a6285cb419b2da339de397
dir: /man/3/rtc/
.TH RTC 3 .SH NAME rtc \- real-time clock and non-volatile memory .SH SYNOPSIS .B bind -b '#r' /dev .PP .B /dev/rtc .br .B /dev/rtcid .br .B /dev/nvram .SH DESCRIPTION The .I rtc device provides access to the real-time clock and any associated non-volatile memory. Physical devices supported include the Mostek MK48T12-15 Zeropower/Timekeeper, the Dallas Semiconductor DS1687 real-time clock, and the IBM PC real-time clock on various platforms. .PP The .B rtc file when read returns the time as a decimal number, expressed as the number of seconds since the epoch, 1 January 1970 00:00 GMT. The clock is set by writing the desired number of seconds since the epoch to the file. Setting the time in this device has no effect on system time returned by .B /dev/time (see .IR cons (3)), which must be set separately if desired. For example, when .I rtc is available .I osinit (see .IR init (8)) uses it to set .BR /dev/time . .PP The .B nvram file provides access to the non-volatile memory commonly implemented by these clock chips. There are no cross-platform standards for the range of addresses that can be safely used by Inferno, or for the content and format of the data. .PP The .B rtcid file holds a decimal number giving the serial number of the device, set during manufacturing. The file exists only if a particular device provides such a number. .SH SOURCE .B /os/*/devrtc.c .SH SEE ALSO .IR cons (3) .SH BUGS The .B rtc file returns seconds but .B /dev/time returns microseconds: it's history.