Stepper Drive Enable Circuit

I have a Mesa 7i96e and some inexpensive Chinese stepper drives. To disable the drive you set the "Enable" input high 5V.

Should I use the E-Stop-out from the 7i96 to set the enable high or simply loop back through the physical E-Stop button N/O contact to provide the 5V?

this depends on you
I personly use the MACHINE ON F2 for the Drives to be enabled and i also use a Realy to get the 5V to ENA or break the circuit non closed as then it can also be to a Simple externel button
Why not E-stop estop is for be a emergency so close everything full power off
and in Normal use you only need to get the Power from the Drives for small adjust or simple time to get somthing done
so no need to close all down

With the negative logic on these inexpensive drives it's not a fail safe condition. A wire break will not be detected.

If an e-stop is initiated do all Mesa I/O go low or do they still function normally.

E-Stop behaviour is entirely determined by your external wiring and
hal setup. That is, there in no default hardware I/O connection to
E-Stop unless its setup in the hal file

Start-up state and state after shutdown/host crash of Mesa cards
is predictable (for example the SSRs on a 7i96 will all be off at power up
or LinuxCNC shutdown or say loss of communication with the host)

PCW wrote:

Start-up state and state after shutdown/host crash of Mesa cards
is predictable (for example the SSRs on a 7i96 will all be off at power up
or LinuxCNC shutdown or say loss of communication with the host)

I understand now. That's what I was getting at, the I/O state after an abnormal event including E-Stop.

I guess I could add an ice-cube relay to invert the drive enable Eh! maybe I'll just leave it enabled all the time

Not sure what the drive enable gets you with a step drive
In fact a step motor may stop faster enabled than disabled
when the pulse stream stops (as would happen with and Estop or watchdog bite)