227 lines
9.1 KiB
ReStructuredText
227 lines
9.1 KiB
ReStructuredText
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Kernel driver vt1211
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====================
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Supported chips:
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* VIA VT1211
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Prefix: 'vt1211'
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Addresses scanned: none, address read from Super-I/O config space
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Datasheet: Provided by VIA upon request and under NDA
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Authors: Juerg Haefliger <juergh@gmail.com>
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This driver is based on the driver for kernel 2.4 by Mark D. Studebaker and
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its port to kernel 2.6 by Lars Ekman.
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Thanks to Joseph Chan and Fiona Gatt from VIA for providing documentation and
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technical support.
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Module Parameters
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-----------------
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* uch_config: int
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Override the BIOS default universal channel (UCH)
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configuration for channels 1-5.
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Legal values are in the range of 0-31. Bit 0 maps to
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UCH1, bit 1 maps to UCH2 and so on. Setting a bit to 1
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enables the thermal input of that particular UCH and
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setting a bit to 0 enables the voltage input.
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* int_mode: int
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Override the BIOS default temperature interrupt mode.
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The only possible value is 0 which forces interrupt
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mode 0. In this mode, any pending interrupt is cleared
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when the status register is read but is regenerated as
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long as the temperature stays above the hysteresis
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limit.
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Be aware that overriding BIOS defaults might cause some unwanted side effects!
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Description
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-----------
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The VIA VT1211 Super-I/O chip includes complete hardware monitoring
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capabilities. It monitors 2 dedicated temperature sensor inputs (temp1 and
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temp2), 1 dedicated voltage (in5) and 2 fans. Additionally, the chip
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implements 5 universal input channels (UCH1-5) that can be individually
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programmed to either monitor a voltage or a temperature.
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This chip also provides manual and automatic control of fan speeds (according
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to the datasheet). The driver only supports automatic control since the manual
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mode doesn't seem to work as advertised in the datasheet. In fact I couldn't
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get manual mode to work at all! Be aware that automatic mode hasn't been
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tested very well (due to the fact that my EPIA M10000 doesn't have the fans
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connected to the PWM outputs of the VT1211 :-().
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The following table shows the relationship between the vt1211 inputs and the
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sysfs nodes.
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=============== ============== =========== ================================
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Sensor Voltage Mode Temp Mode Default Use (from the datasheet)
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=============== ============== =========== ================================
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Reading 1 temp1 Intel thermal diode
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Reading 3 temp2 Internal thermal diode
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UCH1/Reading2 in0 temp3 NTC type thermistor
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UCH2 in1 temp4 +2.5V
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UCH3 in2 temp5 VccP (processor core)
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UCH4 in3 temp6 +5V
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UCH5 in4 temp7 +12V
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+3.3V in5 Internal VCC (+3.3V)
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=============== ============== =========== ================================
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Voltage Monitoring
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------------------
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Voltages are sampled by an 8-bit ADC with a LSB of ~10mV. The supported input
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range is thus from 0 to 2.60V. Voltage values outside of this range need
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external scaling resistors. This external scaling needs to be compensated for
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via compute lines in sensors.conf, like:
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compute inx @*(1+R1/R2), @/(1+R1/R2)
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The board level scaling resistors according to VIA's recommendation are as
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follows. And this is of course totally dependent on the actual board
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implementation :-) You will have to find documentation for your own
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motherboard and edit sensors.conf accordingly.
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============= ====== ====== ========= ============
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Expected
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Voltage R1 R2 Divider Raw Value
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============= ====== ====== ========= ============
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+2.5V 2K 10K 1.2 2083 mV
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VccP --- --- 1.0 1400 mV [1]_
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+5V 14K 10K 2.4 2083 mV
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+12V 47K 10K 5.7 2105 mV
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+3.3V (int) 2K 3.4K 1.588 3300 mV [2]_
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+3.3V (ext) 6.8K 10K 1.68 1964 mV
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============= ====== ====== ========= ============
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.. [1] Depending on the CPU (1.4V is for a VIA C3 Nehemiah).
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.. [2] R1 and R2 for 3.3V (int) are internal to the VT1211 chip and the driver
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performs the scaling and returns the properly scaled voltage value.
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Each measured voltage has an associated low and high limit which triggers an
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alarm when crossed.
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Temperature Monitoring
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----------------------
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Temperatures are reported in millidegree Celsius. Each measured temperature
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has a high limit which triggers an alarm if crossed. There is an associated
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hysteresis value with each temperature below which the temperature has to drop
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before the alarm is cleared (this is only true for interrupt mode 0). The
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interrupt mode can be forced to 0 in case the BIOS doesn't do it
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automatically. See the 'Module Parameters' section for details.
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All temperature channels except temp2 are external. Temp2 is the VT1211
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internal thermal diode and the driver does all the scaling for temp2 and
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returns the temperature in millidegree Celsius. For the external channels
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temp1 and temp3-temp7, scaling depends on the board implementation and needs
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to be performed in userspace via sensors.conf.
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Temp1 is an Intel-type thermal diode which requires the following formula to
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convert between sysfs readings and real temperatures:
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compute temp1 (@-Offset)/Gain, (@*Gain)+Offset
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According to the VIA VT1211 BIOS porting guide, the following gain and offset
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values should be used:
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=============== ======== ===========
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Diode Type Offset Gain
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=============== ======== ===========
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Intel CPU 88.638 0.9528
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65.000 0.9686 [3]_
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VIA C3 Ezra 83.869 0.9528
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VIA C3 Ezra-T 73.869 0.9528
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=============== ======== ===========
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.. [3] This is the formula from the lm_sensors 2.10.0 sensors.conf file. I don't
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know where it comes from or how it was derived, it's just listed here for
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completeness.
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Temp3-temp7 support NTC thermistors. For these channels, the driver returns
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the voltages as seen at the individual pins of UCH1-UCH5. The voltage at the
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pin (Vpin) is formed by a voltage divider made of the thermistor (Rth) and a
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scaling resistor (Rs)::
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Vpin = 2200 * Rth / (Rs + Rth) (2200 is the ADC max limit of 2200 mV)
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The equation for the thermistor is as follows (google it if you want to know
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more about it)::
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Rth = Ro * exp(B * (1 / T - 1 / To)) (To is 298.15K (25C) and Ro is the
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nominal resistance at 25C)
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Mingling the above two equations and assuming Rs = Ro and B = 3435 yields the
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following formula for sensors.conf::
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compute tempx 1 / (1 / 298.15 - (` (2200 / @ - 1)) / 3435) - 273.15,
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2200 / (1 + (^ (3435 / 298.15 - 3435 / (273.15 + @))))
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Fan Speed Control
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-----------------
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The VT1211 provides 2 programmable PWM outputs to control the speeds of 2
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fans. Writing a 2 to any of the two pwm[1-2]_enable sysfs nodes will put the
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PWM controller in automatic mode. There is only a single controller that
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controls both PWM outputs but each PWM output can be individually enabled and
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disabled.
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Each PWM has 4 associated distinct output duty-cycles: full, high, low and
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off. Full and off are internally hard-wired to 255 (100%) and 0 (0%),
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respectively. High and low can be programmed via
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pwm[1-2]_auto_point[2-3]_pwm. Each PWM output can be associated with a
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different thermal input but - and here's the weird part - only one set of
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thermal thresholds exist that controls both PWMs output duty-cycles. The
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thermal thresholds are accessible via pwm[1-2]_auto_point[1-4]_temp. Note
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that even though there are 2 sets of 4 auto points each, they map to the same
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registers in the VT1211 and programming one set is sufficient (actually only
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the first set pwm1_auto_point[1-4]_temp is writable, the second set is
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read-only).
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========================== =========================================
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PWM Auto Point PWM Output Duty-Cycle
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========================== =========================================
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pwm[1-2]_auto_point4_pwm full speed duty-cycle (hard-wired to 255)
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pwm[1-2]_auto_point3_pwm high speed duty-cycle
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pwm[1-2]_auto_point2_pwm low speed duty-cycle
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pwm[1-2]_auto_point1_pwm off duty-cycle (hard-wired to 0)
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========================== =========================================
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========================== =================
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Temp Auto Point Thermal Threshold
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========================== =================
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pwm[1-2]_auto_point4_temp full speed temp
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pwm[1-2]_auto_point3_temp high speed temp
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pwm[1-2]_auto_point2_temp low speed temp
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pwm[1-2]_auto_point1_temp off temp
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========================== =================
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Long story short, the controller implements the following algorithm to set the
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PWM output duty-cycle based on the input temperature:
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=================== ======================= ========================
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Thermal Threshold Output Duty-Cycle Output Duty-Cycle
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(Rising Temp) (Falling Temp)
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=================== ======================= ========================
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- full speed duty-cycle full speed duty-cycle
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full speed temp
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- high speed duty-cycle full speed duty-cycle
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high speed temp
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- low speed duty-cycle high speed duty-cycle
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low speed temp
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- off duty-cycle low speed duty-cycle
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off temp
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=================== ======================= ========================
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