Does the ADT7420 have timeout function?
If the master CPU power off when ADT7420 output the data, does the ADT7420 open the I2C bus?
There is only one way to reset the ADT7420 during normal operation, i.e. without a power cycle, see the ‘RESET’ section of the data sheet. If the master goes into a reset state, then the master must remember to start communications with the ADT7420 again. Since the ADT7420 is a I2C compliant device, there will be no output when the master resets. The ADT7420 has no auto reset after some time.
Kind Regards, Brendan.
Thank you very much for your quick reply. So, during the power of the master off, the AD7420 doesn't open the bus, Right? Or When the power of the master off, AD7420 understands as the master reset and open the bus?
best Regards, James.
Correct, during the power off of the master, the AD7420 open collector output doesn't open the bus if it was active. That is due to the fact that there is no clock and the ADT7420 output may be in an active state. The application software will need to take account of this possibility. After CPU power up, the ADT7420 routine would first test communications by requesting the ID, send another clock to get the AADT7420 to release the bus, then issue a rest command, and start again. It is always necessary for the application software to implement error detection and correction for all parts on the system.
Thank you very much. I could understand about I2C well.
Best Regards, James.
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