Lines Matching +full:one +full:- +full:time +full:- +full:programmable

2 Real Time Clock (RTC) Drivers for Linux
5 When Linux developers talk about a "Real Time Clock", they usually mean
6 something that tracks wall clock time and is battery backed so that it
8 the local time zone or daylight savings time -- unless they dual boot
9 with MS-Windows -- but will instead be set to Coordinated Universal Time
10 (UTC, formerly "Greenwich Mean Time").
12 The newest non-PC hardware tends to just count seconds, like the time(2)
13 system call reports, but RTCs also very commonly represent time using
14 the Gregorian calendar and 24 hour time, as reported by gmtime(3).
16 Linux has two largely-compatible userspace RTC API families you may
20 	so it's not very portable to non-x86 systems.
32 be able to schedule one any time in the upcoming century.
35 Old PC/AT-Compatible driver:  /dev/rtc
36 --------------------------------------
38 All PCs (even Alpha machines) have a Real Time Clock built into them.
41 clock that keeps the date and time while your computer is turned off.
44 a few ways (enabling longer alarm periods, and wake-from-hibernate).
52 subset of the three programmable values, meaning that it could be set to
59 the type of interrupt (update-done, alarm-rang, or periodic) that was
61 the last read.  Status information is reported through the pseudo-file
63 built in locking so that only one process is allowed to have the /dev/rtc
64 interface open at a time.
67 select(2) on /dev/rtc -- either will block/stop the user process until
69 reasonably high frequency data acquisition where one doesn't want to
75 typical 486-33 running a tight read loop on /dev/rtc will start to suffer
83 an evil user generating lots of IRQs on a slow 386sx-16, where it might have
85 a different value to /proc/sys/dev/rtc/max-user-freq. Note that the
89 Also, if the kernel time is synchronized with an external source, the 
90 kernel will write the time back to the CMOS clock every 11 minutes. In 
93 don't synchronize the kernel time with an external source (via ntp or
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111 Because Linux supports many non-ACPI and non-PC platforms, some of which
112 have more than one RTC style clock, it needed a more portable solution
113 than expecting a single battery-backed MC146818 clone on every system.
128 integrated into embeddable system-on-chip (SOC) processors to discrete chips
130 even support for PC-style RTCs ... including the features exposed on newer PCs
133 The new framework also removes the "one RTC per system" restriction.  For
134 example, maybe the low-power battery-backed RTC is a discrete I2C chip, but
136 the system clock from the discrete RTC, but use the integrated one for all