.\"
.\" Copyright (c) 2015 Luiz Otavio O Souza <loos@freebsd.org>
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.Dd December 10, 2024
.Dt DS1307 4
.Os
.Sh NAME
.Nm ds1307
.Nd 64 x 8, serial, i2c real-time clock (RTC)
.Sh SYNOPSIS
.Cd "device iic"
.Cd "device iicbus"
.Cd "device ds1307"
.Sh DESCRIPTION
The
.Nm
serial real-time clock (RTC) is a low-power, full binary-coded decimal (BCD)
clock/calendar plus 56 bytes of NV SRAM.
.Pp
The
.Nm
has a built-in power-sense circuit that detects power failures and
automatically switches to the backup supply.
Timekeeping operation continues while the part operates from the backup supply.
.Pp
Access to
.Nm
settings is made with the
.Xr sysctl 8
interface:
.Bd -literal
dev.ds1307.0.%desc: Maxim DS1307 RTC
dev.ds1307.0.%driver: ds1307
dev.ds1307.0.%location: addr=0xd0
dev.ds1307.0.%pnpinfo: name=rtc compat=maxim,ds1307
dev.ds1307.0.%parent: iicbus1
dev.ds1307.0.sqwe: 1
dev.ds1307.0.sqw_freq: 32768
dev.ds1307.0.sqw_out: 0
.Ed
.Bl -tag -width ".Va dev.ds1307.%d.sqw_freq"
.It Va dev.ds1307.%d.sqwe
If set to 1, the SQW pin drives a square-wave of
.Va dev.ds1307.%d.sqw_freq
frequency.
If set to 0, the output level of SQW pin is controlled by
.Va dev.ds1307.%d.sqw_out .
.It Va dev.ds1307.%d.sqw_freq
Select the frequency of the SQW pin when the square-wave output is enabled on
.Va dev.ds1307.%d.sqwe .
It can be set to 1, 4096, 8192 and 32768.
.It Va dev.ds1307.%d.sqw_out
Set the output level of the SQW pin when
.Va dev.ds1307.%d.sqwe
is set to 0.
.El
.Pp
Please check the
.Nm
datasheet for more details.
.Pp
On a
.Xr device.hints 5
based system, such as
.Li MIPS ,
these values are configurable for
.Nm :
.Bl -tag -width ".Va hint.ds1307.%d.addr"
.It Va hint.ds1307.%d.at
The
.Xr iicbus 4
that the
.Nm
is connected to.
.It Va hint.ds1307.%d.addr
The i2c address of
.Nm .
.El
.Pp
On a
.Xr FDT 4
based system the following properties must be set:
.Bl -tag -width ".Va compatible"
.It Va compatible
Must always be set to "dallas,ds1307" or "maxim,ds1307".
.It Va reg
The i2c address of
.Nm .
The default address for
.Nm
is 0xd0.
.El
.Sh SEE ALSO
.Xr fdt 4 ,
.Xr iic 4 ,
.Xr iicbus 4 ,
.Xr sysctl 8
.Sh HISTORY
The
.Nm
driver first appeared in
.Fx 11.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver and this manual page were written by
.An Luiz Otavio O Souza Aq Mt loos@FreeBSD.org .