Encoder count error flag

Where can I find the definition of the encoder count error flag? Under what circumstances will this bit be set? The corresponding variable is M118 for encoder 1.

 

I know we are in the Deltatau forum, but I still hope there is someone can help.

 

I checked the manuals ,there is only one section relevant to this problem, that is the Encoder SCLK frequency, which is specified by I 7003, now my encoder pulse frequency is 5 MHZ, As is stated in the manual, the Encoder SCLK frequency should be at least four times larger than the pulse frequency. so I set I 7003 to 2556, which means the SCLK frequency is 39.14MHZ, obviously, that is far more enough, but the encoder count error flag M118 still jumps to 1 after I set it to 0 from the Terminal Window, and I can read from the Position Window that the position value for motor 1 is fluctuating, about 10 counts, sometimes larger.

Our linear motor is stay afloat; there is an air film beneath.

As for the EMI, we use the shielded twisted pair cable for the encoder and the controller, the shield case has been grounded.

 

Analysis for this problem both from hardware and software perspective (mainly Variables setting) will be very welcome.

Thank you all!

 

Delta Tau's ASIC is checking for "acceptable" transition between the quadrature states of A and B inputs. As long as all transitions are "acceptable" then Mx18 stays low. Once an incorrect transition happens the Mx18 is set to 1 and stays until reset by user or until DSPGate is rest. "Acceptable" transitions are:

 

A:Low  B:Low     to    A:Low  B:High  and reverse
A:Low  B:High    to    A:High B:High  and reverse
A:High B:High    to    A:High B:Low   and reverse
A:High B:Low     to    A:Low  B:Low   and reverse

Make sure the encoder cable shield is only grounded on the controller side and not connected to motor/encoder on the other end. Also, make sure the motor cable shield is connected at both ends to ground and motor chassis.

 

Do you get the encoder count error even when the amplifier is killed?

Unfortunately we have, I have observed the pulse with an oscilloscope, it was a square wave.

Sina, could you please tell me where did you get this acceptable transition table?

I have searched in my manuals, no results. Is there any other info were given in that section?

The "acceptable" transitions for a quadrature is not documented in any Delta Tau published document. This is purely based upon definition of quadrature feedback signal. Any other transition would be indicating a missed step, rendering the position counter wrong.

 

Sina, thank you. Do you have any good idea on how to check my encoder transition signals to see if it has illegal transitions or not?