Mesa card address syntax

Hi.

I have a mill which was retrofitted a few years ago with a 5i24 and three 7i84's.
For my own interest I would like to decipher one part of the syntax when accessing pins.

A typical pin from the HAL file is:

hm2_5i24.0.7i84.0.1.output-05

so I suspect the section "5i24.0" refers to the first 5i24 i.e. the zero numbered 5i24 board (in this case there is only one)
then "7i84.0.1" where given that there are three other 7i84 boards the "1" at the end of this phrase refers to the second 7i84 board etc.

What I cannot decipher is what the middle 0 refers to i.e. between 7i84. and .1
hm2_5i24.0.7i84.0.1.output-05

In the same way this address:
hm2_7i76e.0.7i76.0.0.output-07
what does the middle zero i.e. hm2_7i76e.0.7i76.0.0.output-07 refer to?

Thanks,
Marty.

That is the "port" address
The host side of the sserial interface is divided into 1 to 4 "ports" numbered 0..3
each port can have up to 8 channels for a maximum of 32 connected devices

The sserial manual page as a little information about this

There is an alternate numbering scheme you can invoke that uses the sserial devices unit number instead of port/channel addressing.This has the advantage that you can swap sserial CAT 5 cables around without changing the I/O structure.