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diff --git a/Documentation/i2c/chips/lm80 b/Documentation/i2c/chips/lm80 new file mode 100644 index 000000000000..cb5b407ba3e6 --- /dev/null +++ b/Documentation/i2c/chips/lm80 @@ -0,0 +1,56 @@ +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. |