Based on kernel version 3.9. Page generated on 2013-05-02 23:07 EST.
1 Kernel driver lm80 2 ================== 3 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/ 15 16 Authors: 17 Frodo Looijaard <email@example.com>, 18 Philip Edelbrock <firstname.lastname@example.org> 19 20 Description 21 ----------- 22 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. 28 29 The LM80 implements one temperature sensor, two fan rotation speed sensors, 30 seven voltage sensors, alarms, and some miscellaneous stuff. 31 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. 40 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. 47 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. 54 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. 61 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.