the EL_POS register can not be written when the motor is stopped, is the document wrong?

[ile ile]

Posted on October 11, 2017 at 22:50

Hi,

In this document:

https://my.st.com/content/ccc/resource/technical/document/datasheet/3f/48/e2/37/6b/ac/4c/f5/DM00090983.pdf/files/DM00090983.pdf/jcr:content/translations/en.DM00090983.pdf

The EL_POS register is claimed to be written when the motor is stopped (remark WS).

The section 11.1.2 says: 'Any attempt to write the register when the motor is running causes the command to be ignored and the CMD_ERROR flag to rise'

But when I write EL_POS when the motor is stopped ( the motor is NOT running), the command is ignored and the CMD_ERROR flag rises too. I have done some experiments, and found that the EL_POS register could be written only when the motor is in HiZ state.I have no idea if it is my fault or the document is wrong. Any suggestions would be appreciated. Thank you.#powerstep01 #el_pos

[Enrico Poli · Accepted solution]

Posted on October 27, 2017 at 13:49

The register can only be written when the device is in high impedance.

[estie]

Posted on February 04, 2018 at 09:20

So the documentation is incorrect as ile ile suspected.  It incorrectly states that the condition is that the motor be stopped, when in fact the condition is that the driver be in HiZ state.

Motor stopped is indicated by the MOT_STATUS bits in the STATUS register when in fact it is the HiZ bit that is relevant.

That should be corrected.