ATV network fault reset

[clintFromVa]

I've got an ATV 71 drive with an Ethernet card.  We are using the 2-wire I/O profile.  There is a Fast-stop contact wired to LI5 which causes EPF1, as intended.  Resetting the fault requires first configuring register 7124, rSF, with value 162.  We did this by the keypad.

Actually resetting the fault requires writing to register 8601, CMd, "0", followed by "12".  Here is the problem; writing to ONLY 8601 causes Modbus exception 4.  Writing to 8600 & 8601 works.

FWIW, writing speed reference to 8602 alone works.

What is register 8600?  Is there some other way to deal with this?

[clintFromVa]

Update:
Rumor has it that writing both #8601 and #8602 simultaneously will work.  It didn't for me.  I still have to write #8600 to avoid the Modbus error #4.

[jeromerives]

if you use an ethernet card you have to assign C302(Bit 2 Com module ctrl word)(value 210) to RST.

Also the CMD word adress is 8501 and not 8601.

Then to reset you have to set the bit2 to TRUE