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- Kernel driver lm63
- ==================
- Supported chips:
- * National Semiconductor LM63
- Prefix: 'lm63'
- Addresses scanned: I2C 0x4c
- Datasheet: Publicly available at the National Semiconductor website
- http://www.national.com/pf/LM/LM63.html
- * National Semiconductor LM64
- Prefix: 'lm64'
- Addresses scanned: I2C 0x18 and 0x4e
- Datasheet: Publicly available at the National Semiconductor website
- http://www.national.com/pf/LM/LM64.html
- Author: Jean Delvare <khali@linux-fr.org>
- Thanks go to Tyan and especially Alex Buckingham for setting up a remote
- access to their S4882 test platform for this driver.
- http://www.tyan.com/
- Description
- -----------
- The LM63 is a digital temperature sensor with integrated fan monitoring
- and control.
- The LM63 is basically an LM86 with fan speed monitoring and control
- capabilities added. It misses some of the LM86 features though:
- - No low limit for local temperature.
- - No critical limit for local temperature.
- - Critical limit for remote temperature can be changed only once. We
- will consider that the critical limit is read-only.
- The datasheet isn't very clear about what the tachometer reading is.
- An explanation from National Semiconductor: The two lower bits of the read
- value have to be masked out. The value is still 16 bit in width.
- All temperature values are given in degrees Celsius. Resolution is 1.0
- degree for the local temperature, 0.125 degree for the remote temperature.
- The fan speed is measured using a tachometer. Contrary to most chips which
- store the value in an 8-bit register and have a selectable clock divider
- to make sure that the result will fit in the register, the LM63 uses 16-bit
- value for measuring the speed of the fan. It can measure fan speeds down to
- 83 RPM, at least in theory.
- Note that the pin used for fan monitoring is shared with an alert out
- function. Depending on how the board designer wanted to use the chip, fan
- speed monitoring will or will not be possible. The proper chip configuration
- is left to the BIOS, and the driver will blindly trust it.
- A PWM output can be used to control the speed of the fan. The LM63 has two
- PWM modes: manual and automatic. Automatic mode is not fully implemented yet
- (you cannot define your custom PWM/temperature curve), and mode change isn't
- supported either.
- The lm63 driver will not update its values more frequently than every
- second; reading them more often will do no harm, but will return 'old'
- values.
- The LM64 is effectively an LM63 with GPIO lines. The driver does not
- support these GPIO lines at present.
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