SSI Overflow Mode

When is SSI Overflow Mode selected?

A transducer overflow is triggered if all the bits in the SSI value from the feedback are ones.

Bit 21
A transducer overflow is triggered if bit 21 is 1.

Questions about the Ones and Bit 21 modes

The value returned by the sensor is 1, why is it considered an overflow?
I think the overflow should be the jump from the maximum value to the minimum value.

Bit 21
If the sensor is 25 bits, it should be normal if the 21 bits are 1.
Why choose 21 bits?

The SSI Overflow Mode is to ensure full compatibility with most transducers on the market. Some transducers will set all bits to Zero or One when no magnet is detected. In turn, Bit 21 is used on certain older Balluff transducers to signify no magnet being detected. Unless your transducer datasheet specifies otherwise, most newer transducers would use the ‘None’ option.