About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / hwmon / lm80

Custom Search

Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.

1	Kernel driver lm80
2	==================
4	Supported chips:
5	  * National Semiconductor LM80
6	    Prefix: 'lm80'
7	    Addresses scanned: I2C 0x28 - 0x2f
8	    Datasheet: Publicly available at the National Semiconductor website
9	               http://www.national.com/
10	  * National Semiconductor LM96080
11	    Prefix: 'lm96080'
12	    Addresses scanned: I2C 0x28 - 0x2f
13	    Datasheet: Publicly available at the National Semiconductor website
14	               http://www.national.com/
16	Authors:
17	        Frodo Looijaard <frodol@dds.nl>,
18	        Philip Edelbrock <phil@netroedge.com>
20	Description
21	-----------
23	This driver implements support for the National Semiconductor LM80.
24	It is described as a 'Serial Interface ACPI-Compatible Microprocessor
25	System Hardware Monitor'. The LM96080 is a more recent incarnation,
26	it is pin and register compatible, with a few additional features not
27	yet supported by the driver.
29	The LM80 implements one temperature sensor, two fan rotation speed sensors,
30	seven voltage sensors, alarms, and some miscellaneous stuff.
32	Temperatures are measured in degrees Celsius. There are two sets of limits
33	which operate independently. When the HOT Temperature Limit is crossed,
34	this will cause an alarm that will be reasserted until the temperature
35	drops below the HOT Hysteresis. The Overtemperature Shutdown (OS) limits
36	should work in the same way (but this must be checked; the datasheet
37	is unclear about this). Measurements are guaranteed between -55 and
38	+125 degrees. The current temperature measurement has a resolution of
39	0.0625 degrees; the limits have a resolution of 1 degree.
41	Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
42	triggered if the rotation speed has dropped below a programmable limit. Fan
43	readings can be divided by a programmable divider (1, 2, 4 or 8) to give
44	the readings more range or accuracy. Not all RPM values can accurately be
45	represented, so some rounding is done. With a divider of 2, the lowest
46	representable value is around 2600 RPM.
48	Voltage sensors (also known as IN sensors) report their values in volts.
49	An alarm is triggered if the voltage has crossed a programmable minimum
50	or maximum limit. Note that minimum in this case always means 'closest to
51	zero'; this is important for negative voltage measurements. All voltage
52	inputs can measure voltages between 0 and 2.55 volts, with a resolution
53	of 0.01 volt.
55	If an alarm triggers, it will remain triggered until the hardware register
56	is read at least once. This means that the cause for the alarm may
57	already have disappeared! Note that in the current implementation, all
58	hardware registers are read whenever any data is read (unless it is less
59	than 2.0 seconds since the last update). This means that you can easily
60	miss once-only alarms.
62	The LM80 only updates its values each 1.5 seconds; reading it more often
63	will do no harm, but will return 'old' values.
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.