National semiconductor LM75 temperature sensor

The National semiconductor LM75 is an temperature sensor with I2C Interface.

Device Bugs

The National Semiconductor can go into a state where it blocks the bus by pulling SDA line to low forever, no matter how many clock cycles are driven on the SCL line. This happens if you create a start and a stop condition when the master acknowledges a temperature read. This is of course illegal but i found a case where this happened. The LM75 seems to release SDA in normal cases by shifting out 0xff on the I2C bus if you read more more than 2 Bytes (The temperature value is 2 Bytes). It seems like the misplaced stop condition during the ack phase results in a stopped internal bit counter before the FIFO starts sending 0xff. The only way to bring the LM75 to a normal state is to remove power. Don't use the National Semiconductor LM75 in noisy environments. Try an other vendor.

Emulator bugs / Missing features