NAME

rtc — non-volatile RAM / real time clock

SYNOPSIS

device genclock
device mc146818
device rtc

DESCRIPTION

The rtc driver is a front-end for the machine-independent Motorola MC146818 and compatible clocks driver. The Motorola MC146818 and compatible clocks driver provides access to the real time clock part of the chips it supports to FreeBSD by interfacing with the generic clock code.

Dallas / Maxim Semiconductor DS1287 chips (those are compatible to the Motorola MC146818 clocks) are found on the ISA bus of UltraSPARC II systems and the EBus bus of UltraSPARC III systems.

DIAGNOSTICS

The following driver specific error message may be reported:

mc146818_attach_attach: battery low

The device signals that its battery is low and should be replaced. The rtc driver refused to attach the device in this case as the time in the real time clock is probably invalid. This gives the generic clock code the chance to use another device as the system real time clock that otherwise would not have been chosen.

SEE ALSO

ebus(4), eeprom(4)

HISTORY

The rtc driver first appeared in FreeBSD 5.4.

AUTHORS

The rtc driver was written by Marius Strobl <marius@FreeBSD.org>.