firmware 5i25,7i85,8i20 brushless servo drive

The first thing you need is logic power to the 8I20.
I would use the external (TB1) power option.
This means 8I20 W2 should be down and 7 to 48VDC (24VDC is a good choice)
needs to be applied to the 8I20 TB1 pins 1 and 2 (8I20man.pdf page 2 and 3)

The next thing is that a serial cable needs to connect from the 7I85 to the 8I20
(7I85man.pdf pages 7 and 10)

Thanks , I will get right to studying the manual.

I hooked it up , like you said. I used a 12v wall wart type transformer and connected to logic power + and - on 8i20 servo motor drive.

I plugged the CAT5e cable in and connected the wires at the other end to 7i85 tb2 pins 9 thru 16.

Page 10 7i85 indicates three options -pins9 thru 16
pins1thru 8
pins17 thru 24

I can't find any information that tells me which set to use so I just picked one at random.

the following LEDs are on-pwr, lv status,iso pwr,fault

status and hv are off.

I tried connecting the same 12v supply also to enable in +and- but that did not make the red fault led go off.

I get the same error- pin amp enable does not exist.

I plugged the CAT5e cable in and connected the wires at the other end to 7i85 tb2 pins 9 thru 16.

Page 10 7i85 indicates three options -pins9 thru 16
pins1thru 8
pins17 thru 24

I can't find any information that tells me which set to use so I just picked one at random.

The picture on 7I85 manual page 3 and connector pinouts on page 7 and 8 indicate which serial channel connect to which terminal block (you have connected to serial 0 which make sense to start with)

the following LEDs are on-pwr, lv status,iso pwr,fault

status and hv are off.

I tried connecting the same 12v supply also to enable in +and- but that did not make the red fault led go off.

OK thats good that means the 8I20- logic power is on. You will need the drive enable powered to start the drive but the fault LED will not go out until communications are established with LinuxCNC. When this happens you should see the red fault LED extingush and a green status LED start blinking

If this does not happen it can be a number of things, most likely serial cable or HAL file issues.

Do I need to ground the negative side of the 12v wall wart power supply? The parts are just sitting on my desk.

It should not matter if the 12V supply is grounded

on tb2 is number 1 at the bottom and 24 at the top?

Pin 1 is at the bottom (marked with a square and a small '1' on the drawing on page 3)

IT WORKS!

Despite being super careful, I had it connected upside down.

Thanks for your patient help. I have lots of features to check out now.