Some encoders send in addition to the position values ec40 and ec41 an error bit
(often called Power Fail Bit PFB) which is 0 in normal operation and becomes 1
when the encoder detects an error status, e.g. operating voltage too low.
When a PFB is set, an additional clock is automatically output to read this bit. I.e.
ec40 and ec41 remain unaffected.
If the encoder has a PFB and the data word is gray coded, the PFB must also be
gray coded. In contrast, this variant is not supported: Only the position value is
gray coded and then the PFB is attached.
The fir tree data format is rarely found today. Most encoders have the serial-right
data format, so this should be set first.
SSI clock frequency ec43 SSI clock freq.