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Diffstat (limited to 'Documentation/hwmon/lm77')
| -rw-r--r-- | Documentation/hwmon/lm77 | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/Documentation/hwmon/lm77 b/Documentation/hwmon/lm77 index 57c3a46d637..bfc915fe363 100644 --- a/Documentation/hwmon/lm77 +++ b/Documentation/hwmon/lm77 @@ -18,5 +18,21 @@ sensor incorporates a band-gap type temperature sensor, 10-bit ADC, and a digital comparator with user-programmable upper and lower limit values. -Limits can be set through the Overtemperature Shutdown register and -Hysteresis register. +The LM77 implements 3 limits: low (temp1_min), high (temp1_max) and +critical (temp1_crit.) It also implements an hysteresis mechanism which +applies to all 3 limits. The relative difference is stored in a single +register on the chip, which means that the relative difference between +the limit and its hysteresis is always the same for all 3 limits. + +This implementation detail implies the following: +* When setting a limit, its hysteresis will automatically follow, the + difference staying unchanged. For example, if the old critical limit + was 80 degrees C, and the hysteresis was 75 degrees C, and you change + the critical limit to 90 degrees C, then the hysteresis will + automatically change to 85 degrees C. +* All 3 hysteresis can't be set independently. We decided to make + temp1_crit_hyst writable, while temp1_min_hyst and temp1_max_hyst are + read-only. Setting temp1_crit_hyst writes the difference between + temp1_crit_hyst and temp1_crit into the chip, and the same relative + hysteresis applies automatically to the low and high limits. +* The limits should be set before the hysteresis. |