YSI DIQ/S 182 XT-4-PR - Manual (Page 127)

System 182 XT-4 PROFIBUS connection
7 - 11 ba76027e01 02/2012
Measured value status The data for measured value status of the main and secondary
measured values are encoded jointly into a single byte. Bits 7-4 encode
the status of the main measured value, bits 3-0 encode the status of the
secondary measured value.
Other data All other data always consist of only a single byte (Int8).