| Kernel driver lm77 |
| ================== |
| |
| Supported chips: |
| |
| * National Semiconductor LM77 |
| |
| Prefix: 'lm77' |
| |
| Addresses scanned: I2C 0x48 - 0x4b |
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| Datasheet: Publicly available at the National Semiconductor website |
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| http://www.national.com/ |
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| |
| Author: Andras BALI <drewie@freemail.hu> |
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| Description |
| ----------- |
| |
| The LM77 implements one temperature sensor. The temperature |
| sensor incorporates a band-gap type temperature sensor, |
| 10-bit ADC, and a digital comparator with user-programmable upper |
| and lower limit values. |
| |
| 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. |
