Root/
1 | Kernel driver lm78 |
2 | ================== |
3 | |
4 | Supported chips: |
5 | * National Semiconductor LM78 / LM78-J |
6 | Prefix: 'lm78' |
7 | Addresses scanned: I2C 0x28 - 0x2f, ISA 0x290 (8 I/O ports) |
8 | Datasheet: Publicly available at the National Semiconductor website |
9 | http://www.national.com/ |
10 | * National Semiconductor LM79 |
11 | Prefix: 'lm79' |
12 | Addresses scanned: I2C 0x28 - 0x2f, ISA 0x290 (8 I/O ports) |
13 | Datasheet: Publicly available at the National Semiconductor website |
14 | http://www.national.com/ |
15 | |
16 | Author: Frodo Looijaard <frodol@dds.nl> |
17 | |
18 | Description |
19 | ----------- |
20 | |
21 | This driver implements support for the National Semiconductor LM78, LM78-J |
22 | and LM79. They are described as 'Microprocessor System Hardware Monitors'. |
23 | |
24 | There is almost no difference between the three supported chips. Functionally, |
25 | the LM78 and LM78-J are exactly identical. The LM79 has one more VID line, |
26 | which is used to report the lower voltages newer Pentium processors use. |
27 | From here on, LM7* means either of these three types. |
28 | |
29 | The LM7* implements one temperature sensor, three fan rotation speed sensors, |
30 | seven voltage sensors, VID lines, alarms, and some miscellaneous stuff. |
31 | |
32 | Temperatures are measured in degrees Celsius. An alarm is triggered once |
33 | when the Overtemperature Shutdown limit is crossed; it is triggered again |
34 | as soon as it drops below the Hysteresis value. A more useful behavior |
35 | can be found by setting the Hysteresis value to +127 degrees Celsius; in |
36 | this case, alarms are issued during all the time when the actual temperature |
37 | is above the Overtemperature Shutdown value. Measurements are guaranteed |
38 | between -55 and +125 degrees, with a resolution of 1 degree. |
39 | |
40 | Fan rotation speeds are reported in RPM (rotations per minute). An alarm is |
41 | triggered if the rotation speed has dropped below a programmable limit. Fan |
42 | readings can be divided by a programmable divider (1, 2, 4 or 8) to give |
43 | the readings more range or accuracy. Not all RPM values can accurately be |
44 | represented, so some rounding is done. With a divider of 2, the lowest |
45 | representable value is around 2600 RPM. |
46 | |
47 | Voltage sensors (also known as IN sensors) report their values in volts. |
48 | An alarm is triggered if the voltage has crossed a programmable minimum |
49 | or maximum limit. Note that minimum in this case always means 'closest to |
50 | zero'; this is important for negative voltage measurements. All voltage |
51 | inputs can measure voltages between 0 and 4.08 volts, with a resolution |
52 | of 0.016 volt. |
53 | |
54 | The VID lines encode the core voltage value: the voltage level your processor |
55 | should work with. This is hardcoded by the mainboard and/or processor itself. |
56 | It is a value in volts. When it is unconnected, you will often find the |
57 | value 3.50 V here. |
58 | |
59 | If an alarm triggers, it will remain triggered until the hardware register |
60 | is read at least once. This means that the cause for the alarm may |
61 | already have disappeared! Note that in the current implementation, all |
62 | hardware registers are read whenever any data is read (unless it is less |
63 | than 1.5 seconds since the last update). This means that you can easily |
64 | miss once-only alarms. |
65 | |
66 | The LM7* only updates its values each 1.5 seconds; reading it more often |
67 | will do no harm, but will return 'old' values. |
68 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9