ede7fbdf52
Part 3: Move the drivers documentation, plus two general documentation files. Note that the patch "adds trailing whitespace", because it does move the files as-is, and some files happen to have trailing whitespace. Signed-off-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
221 lines
10 KiB
Text
221 lines
10 KiB
Text
Kernel driver lm85
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==================
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Supported chips:
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* National Semiconductor LM85 (B and C versions)
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Prefix: 'lm85'
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Addresses scanned: I2C 0x2c, 0x2d, 0x2e
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Datasheet: http://www.national.com/pf/LM/LM85.html
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* Analog Devices ADM1027
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Prefix: 'adm1027'
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Addresses scanned: I2C 0x2c, 0x2d, 0x2e
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Datasheet: http://www.analog.com/en/prod/0,,766_825_ADM1027,00.html
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* Analog Devices ADT7463
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Prefix: 'adt7463'
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Addresses scanned: I2C 0x2c, 0x2d, 0x2e
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Datasheet: http://www.analog.com/en/prod/0,,766_825_ADT7463,00.html
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* SMSC EMC6D100, SMSC EMC6D101
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Prefix: 'emc6d100'
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Addresses scanned: I2C 0x2c, 0x2d, 0x2e
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Datasheet: http://www.smsc.com/main/tools/discontinued/6d100.pdf
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* SMSC EMC6D102
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Prefix: 'emc6d102'
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Addresses scanned: I2C 0x2c, 0x2d, 0x2e
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Datasheet: http://www.smsc.com/main/catalog/emc6d102.html
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Authors:
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Philip Pokorny <ppokorny@penguincomputing.com>,
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Frodo Looijaard <frodol@dds.nl>,
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Richard Barrington <rich_b_nz@clear.net.nz>,
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Margit Schubert-While <margitsw@t-online.de>,
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Justin Thiessen <jthiessen@penguincomputing.com>
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Description
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-----------
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This driver implements support for the National Semiconductor LM85 and
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compatible chips including the Analog Devices ADM1027, ADT7463 and
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SMSC EMC6D10x chips family.
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The LM85 uses the 2-wire interface compatible with the SMBUS 2.0
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specification. Using an analog to digital converter it measures three (3)
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temperatures and five (5) voltages. It has four (4) 16-bit counters for
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measuring fan speed. Five (5) digital inputs are provided for sampling the
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VID signals from the processor to the VRM. Lastly, there are three (3) PWM
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outputs that can be used to control fan speed.
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The voltage inputs have internal scaling resistors so that the following
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voltage can be measured without external resistors:
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2.5V, 3.3V, 5V, 12V, and CPU core voltage (2.25V)
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The temperatures measured are one internal diode, and two remote diodes.
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Remote 1 is generally the CPU temperature. These inputs are designed to
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measure a thermal diode like the one in a Pentium 4 processor in a socket
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423 or socket 478 package. They can also measure temperature using a
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transistor like the 2N3904.
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A sophisticated control system for the PWM outputs is designed into the
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LM85 that allows fan speed to be adjusted automatically based on any of the
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three temperature sensors. Each PWM output is individually adjustable and
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programmable. Once configured, the LM85 will adjust the PWM outputs in
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response to the measured temperatures without further host intervention.
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This feature can also be disabled for manual control of the PWM's.
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Each of the measured inputs (voltage, temperature, fan speed) has
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corresponding high/low limit values. The LM85 will signal an ALARM if any
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measured value exceeds either limit.
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The LM85 samples all inputs continuously. The lm85 driver will not read
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the registers more often than once a second. Further, configuration data is
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only read once each 5 minutes. There is twice as much config data as
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measurements, so this would seem to be a worthwhile optimization.
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Special Features
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----------------
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The LM85 has four fan speed monitoring modes. The ADM1027 has only two.
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Both have special circuitry to compensate for PWM interactions with the
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TACH signal from the fans. The ADM1027 can be configured to measure the
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speed of a two wire fan, but the input conditioning circuitry is different
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for 3-wire and 2-wire mode. For this reason, the 2-wire fan modes are not
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exposed to user control. The BIOS should initialize them to the correct
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mode. If you've designed your own ADM1027, you'll have to modify the
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init_client function and add an insmod parameter to set this up.
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To smooth the response of fans to changes in temperature, the LM85 has an
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optional filter for smoothing temperatures. The ADM1027 has the same
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config option but uses it to rate limit the changes to fan speed instead.
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The ADM1027 and ADT7463 have a 10-bit ADC and can therefore measure
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temperatures with 0.25 degC resolution. They also provide an offset to the
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temperature readings that is automatically applied during measurement.
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This offset can be used to zero out any errors due to traces and placement.
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The documentation says that the offset is in 0.25 degC steps, but in
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initial testing of the ADM1027 it was 1.00 degC steps. Analog Devices has
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confirmed this "bug". The ADT7463 is reported to work as described in the
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documentation. The current lm85 driver does not show the offset register.
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The ADT7463 has a THERM asserted counter. This counter has a 22.76ms
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resolution and a range of 5.8 seconds. The driver implements a 32-bit
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accumulator of the counter value to extend the range to over a year. The
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counter will stay at it's max value until read.
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See the vendor datasheets for more information. There is application note
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from National (AN-1260) with some additional information about the LM85.
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The Analog Devices datasheet is very detailed and describes a procedure for
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determining an optimal configuration for the automatic PWM control.
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The SMSC EMC6D100 & EMC6D101 monitor external voltages, temperatures, and
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fan speeds. They use this monitoring capability to alert the system to out
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of limit conditions and can automatically control the speeds of multiple
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fans in a PC or embedded system. The EMC6D101, available in a 24-pin SSOP
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package, and the EMC6D100, available in a 28-pin SSOP package, are designed
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to be register compatible. The EMC6D100 offers all the features of the
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EMC6D101 plus additional voltage monitoring and system control features.
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Unfortunately it is not possible to distinguish between the package
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versions on register level so these additional voltage inputs may read
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zero. The EMC6D102 features addtional ADC bits thus extending precision
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of voltage and temperature channels.
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Hardware Configurations
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-----------------------
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The LM85 can be jumpered for 3 different SMBus addresses. There are
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no other hardware configuration options for the LM85.
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The lm85 driver detects both LM85B and LM85C revisions of the chip. See the
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datasheet for a complete description of the differences. Other than
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identifying the chip, the driver behaves no differently with regard to
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these two chips. The LM85B is recommended for new designs.
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The ADM1027 and ADT7463 chips have an optional SMBALERT output that can be
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used to signal the chipset in case a limit is exceeded or the temperature
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sensors fail. Individual sensor interrupts can be masked so they won't
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trigger SMBALERT. The SMBALERT output if configured replaces one of the other
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functions (PWM2 or IN0). This functionality is not implemented in current
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driver.
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The ADT7463 also has an optional THERM output/input which can be connected
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to the processor PROC_HOT output. If available, the autofan control
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dynamic Tmin feature can be enabled to keep the system temperature within
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spec (just?!) with the least possible fan noise.
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Configuration Notes
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-------------------
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Besides standard interfaces driver adds following:
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* Temperatures and Zones
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Each temperature sensor is associated with a Zone. There are three
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sensors and therefore three zones (# 1, 2 and 3). Each zone has the following
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temperature configuration points:
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* temp#_auto_temp_off - temperature below which fans should be off or spinning very low.
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* temp#_auto_temp_min - temperature over which fans start to spin.
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* temp#_auto_temp_max - temperature when fans spin at full speed.
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* temp#_auto_temp_crit - temperature when all fans will run full speed.
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* PWM Control
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There are three PWM outputs. The LM85 datasheet suggests that the
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pwm3 output control both fan3 and fan4. Each PWM can be individually
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configured and assigned to a zone for it's control value. Each PWM can be
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configured individually according to the following options.
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* pwm#_auto_pwm_min - this specifies the PWM value for temp#_auto_temp_off
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temperature. (PWM value from 0 to 255)
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* pwm#_auto_pwm_freq - select base frequency of PWM output. You can select
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in range of 10.0 to 94.0 Hz in .1 Hz units.
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(Values 100 to 940).
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The pwm#_auto_pwm_freq can be set to one of the following 8 values. Setting the
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frequency to a value not on this list, will result in the next higher frequency
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being selected. The actual device frequency may vary slightly from this
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specification as designed by the manufacturer. Consult the datasheet for more
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details. (PWM Frequency values: 100, 150, 230, 300, 380, 470, 620, 940)
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* pwm#_auto_pwm_minctl - this flags selects for temp#_auto_temp_off temperature
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the bahaviour of fans. Write 1 to let fans spinning at
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pwm#_auto_pwm_min or write 0 to let them off.
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NOTE: It has been reported that there is a bug in the LM85 that causes the flag
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to be associated with the zones not the PWMs. This contradicts all the
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published documentation. Setting pwm#_min_ctl in this case actually affects all
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PWMs controlled by zone '#'.
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* PWM Controlling Zone selection
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* pwm#_auto_channels - controls zone that is associated with PWM
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Configuration choices:
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Value Meaning
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------ ------------------------------------------------
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1 Controlled by Zone 1
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2 Controlled by Zone 2
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3 Controlled by Zone 3
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23 Controlled by higher temp of Zone 2 or 3
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123 Controlled by highest temp of Zone 1, 2 or 3
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0 PWM always 0% (off)
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-1 PWM always 100% (full on)
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-2 Manual control (write to 'pwm#' to set)
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The National LM85's have two vendor specific configuration
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features. Tach. mode and Spinup Control. For more details on these,
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see the LM85 datasheet or Application Note AN-1260.
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The Analog Devices ADM1027 has several vendor specific enhancements.
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The number of pulses-per-rev of the fans can be set, Tach monitoring
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can be optimized for PWM operation, and an offset can be applied to
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the temperatures to compensate for systemic errors in the
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measurements.
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In addition to the ADM1027 features, the ADT7463 also has Tmin control
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and THERM asserted counts. Automatic Tmin control acts to adjust the
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Tmin value to maintain the measured temperature sensor at a specified
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temperature. There isn't much documentation on this feature in the
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ADT7463 data sheet. This is not supported by current driver.
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