path: root/Documentation/hwmon/lm63
diff options
Diffstat (limited to 'Documentation/hwmon/lm63')
1 files changed, 77 insertions, 0 deletions
diff --git a/Documentation/hwmon/lm63 b/Documentation/hwmon/lm63
new file mode 100644
index 00000000..4d30d209
--- /dev/null
+++ b/Documentation/hwmon/lm63
@@ -0,0 +1,77 @@
+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
+ * National Semiconductor LM96163
+ Prefix: 'lm96163'
+ Addresses scanned: I2C 0x4c
+ Datasheet: Publicly available at the National Semiconductor website
+ http://www.national.com/pf/LM/LM96163.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/
+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. Only the original
+LM63 suffers from this limitation, the LM64 and LM96163 have separate pins
+for fan monitoring and alert out. On the LM64, monitoring is always enabled;
+on the LM96163 it can be disabled.
+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 configured with
+the update_interval sysfs attribute; reading them more often will do no harm,
+but will return 'old' values. Values in the automatic fan control lookup table
+(attributes pwm1_auto_*) have their own independent lifetime of 5 seconds.
+The LM64 is effectively an LM63 with GPIO lines. The driver does not
+support these GPIO lines at present.
+The LM96163 is an enhanced version of LM63 with improved temperature accuracy
+and better PWM resolution. For LM96163, the external temperature sensor type is
+configurable as CPU embedded diode(1) or 3904 transistor(2).