lm80.rst (2880B)
1Kernel driver lm80 2================== 3 4Supported chips: 5 6 * National Semiconductor LM80 7 8 Prefix: 'lm80' 9 10 Addresses scanned: I2C 0x28 - 0x2f 11 12 Datasheet: Publicly available at the National Semiconductor website 13 14 http://www.national.com/ 15 16 * National Semiconductor LM96080 17 18 Prefix: 'lm96080' 19 20 Addresses scanned: I2C 0x28 - 0x2f 21 22 Datasheet: Publicly available at the National Semiconductor website 23 24 http://www.national.com/ 25 26 27Authors: 28 - Frodo Looijaard <frodol@dds.nl>, 29 - Philip Edelbrock <phil@netroedge.com> 30 31Description 32----------- 33 34This driver implements support for the National Semiconductor LM80. 35It is described as a 'Serial Interface ACPI-Compatible Microprocessor 36System Hardware Monitor'. The LM96080 is a more recent incarnation, 37it is pin and register compatible, with a few additional features not 38yet supported by the driver. 39 40The LM80 implements one temperature sensor, two fan rotation speed sensors, 41seven voltage sensors, alarms, and some miscellaneous stuff. 42 43Temperatures are measured in degrees Celsius. There are two sets of limits 44which operate independently. When the HOT Temperature Limit is crossed, 45this will cause an alarm that will be reasserted until the temperature 46drops below the HOT Hysteresis. The Overtemperature Shutdown (OS) limits 47should work in the same way (but this must be checked; the datasheet 48is unclear about this). Measurements are guaranteed between -55 and 49+125 degrees. The current temperature measurement has a resolution of 500.0625 degrees; the limits have a resolution of 1 degree. 51 52Fan rotation speeds are reported in RPM (rotations per minute). An alarm is 53triggered if the rotation speed has dropped below a programmable limit. Fan 54readings can be divided by a programmable divider (1, 2, 4 or 8) to give 55the readings more range or accuracy. Not all RPM values can accurately be 56represented, so some rounding is done. With a divider of 2, the lowest 57representable value is around 2600 RPM. 58 59Voltage sensors (also known as IN sensors) report their values in volts. 60An alarm is triggered if the voltage has crossed a programmable minimum 61or maximum limit. Note that minimum in this case always means 'closest to 62zero'; this is important for negative voltage measurements. All voltage 63inputs can measure voltages between 0 and 2.55 volts, with a resolution 64of 0.01 volt. 65 66If an alarm triggers, it will remain triggered until the hardware register 67is read at least once. This means that the cause for the alarm may 68already have disappeared! Note that in the current implementation, all 69hardware registers are read whenever any data is read (unless it is less 70than 2.0 seconds since the last update). This means that you can easily 71miss once-only alarms. 72 73The LM80 only updates its values each 1.5 seconds; reading it more often 74will do no harm, but will return 'old' values.