SSI encoder with extra status bit.

[pennells]

We have a rather specialized type of SSI encoder which have an extra most-significant bit that specifies the health of the encoder information (IE 18-bit encoder that sends 19 bits of data with the MSB as a health signal). Is there a way to use the encoder information directly in the encoder table while masking off the extra MSB so that the information is correct. I figure that I can read that bit directly from the ACC24E3 data structure but I figure that the extra bit will mess the EncTable reading up when it wraps around.

 

I tried sett the type to 1 and using index2 (right-shift) {13} and index1 (left-shift) {14} to get rid of the MSB but that doesn't appear to work--if the MSB gets set, the position data goes to some small negative value regardless of the other bits. Any ideas of a possible solution?

[Richard Naddaf]

Yes, you should be able to mask it properly. This is a common procedure. Try shifting only left 14 bits (index1) and setting EncTable[x].ScaleFactor=1/exp2(14).

[pennells]

Finally, got this specialized encoder and your solution worked perfectly, thanks.