lm80.rst 2.8 KB

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