ede7fbdf52
Part 3: Move the drivers documentation, plus two general documentation files. Note that the patch "adds trailing whitespace", because it does move the files as-is, and some files happen to have trailing whitespace. Signed-off-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
56 lines
2.5 KiB
Text
56 lines
2.5 KiB
Text
Kernel driver lm80
|
|
==================
|
|
|
|
Supported chips:
|
|
* National Semiconductor LM80
|
|
Prefix: 'lm80'
|
|
Addresses scanned: I2C 0x28 - 0x2f
|
|
Datasheet: Publicly available at the National Semiconductor website
|
|
http://www.national.com/
|
|
|
|
Authors:
|
|
Frodo Looijaard <frodol@dds.nl>,
|
|
Philip Edelbrock <phil@netroedge.com>
|
|
|
|
Description
|
|
-----------
|
|
|
|
This driver implements support for the National Semiconductor LM80.
|
|
It is described as a 'Serial Interface ACPI-Compatible Microprocessor
|
|
System Hardware Monitor'.
|
|
|
|
The LM80 implements one temperature sensor, two fan rotation speed sensors,
|
|
seven voltage sensors, alarms, and some miscellaneous stuff.
|
|
|
|
Temperatures are measured in degrees Celsius. There are two sets of limits
|
|
which operate independently. When the HOT Temperature Limit is crossed,
|
|
this will cause an alarm that will be reasserted until the temperature
|
|
drops below the HOT Hysteresis. The Overtemperature Shutdown (OS) limits
|
|
should work in the same way (but this must be checked; the datasheet
|
|
is unclear about this). Measurements are guaranteed between -55 and
|
|
+125 degrees. The current temperature measurement has a resolution of
|
|
0.0625 degrees; the limits have a resolution of 1 degree.
|
|
|
|
Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
|
|
triggered if the rotation speed has dropped below a programmable limit. Fan
|
|
readings can be divided by a programmable divider (1, 2, 4 or 8) to give
|
|
the readings more range or accuracy. Not all RPM values can accurately be
|
|
represented, so some rounding is done. With a divider of 2, the lowest
|
|
representable value is around 2600 RPM.
|
|
|
|
Voltage sensors (also known as IN sensors) report their values in volts.
|
|
An alarm is triggered if the voltage has crossed a programmable minimum
|
|
or maximum limit. Note that minimum in this case always means 'closest to
|
|
zero'; this is important for negative voltage measurements. All voltage
|
|
inputs can measure voltages between 0 and 2.55 volts, with a resolution
|
|
of 0.01 volt.
|
|
|
|
If an alarm triggers, it will remain triggered until the hardware register
|
|
is read at least once. This means that the cause for the alarm may
|
|
already have disappeared! Note that in the current implementation, all
|
|
hardware registers are read whenever any data is read (unless it is less
|
|
than 2.0 seconds since the last update). This means that you can easily
|
|
miss once-only alarms.
|
|
|
|
The LM80 only updates its values each 1.5 seconds; reading it more often
|
|
will do no harm, but will return 'old' values.
|