Max Amount of Comms Cards In AB 1756-A17 Rack

Is there any limitations on the maximum amount of communication cards in one rack.

for example if i have a 17 slot rack with the following setup can i fill the remaining 14 slots with DNB cards for 14 separate networks

Slot 0 - L63 CPU
Slot 1 -ENBT Ethernet Card
Slot 2 - CNB ControlNet Card
Slot 3 - Spare
Slot 4 - Spare
Slot 5 - Spare
Slot 6 - Spare
Slot 7 - Spare
Slot 8 - Spare
Slot 9 - Spare
ETC.....

Basically you can do that...see the following technote: https://rockwellautomation.custhelp.com/app/answers/detail/a_id/467303

- fuzzy logic

Thanks for the quick reply now to do a bit of digging around to see what the smallest CPU is i can use for this job.

Which leads me to another question if you have an array of 30 Bools that are declared as produced/consumed tags is this classed as 1 connection in the CPU or 30?

Cheers

The second question is easy; you can't define a BOOL tag as a Produced/Consumed Tag. Pack the 30 bits into a DINT datatype, which is the smallest atomic datatype you can use with Produced/Consumed Tags.

There is no pre-set limit to how many communication modules you can have in a chassis, but there will be practical limitations on how much power is available, especially on boot-up, and on how many connections can be made across the other network modules.

The full suite of modules you describe will consume 13.1 amperes at 5V DC, and the biggest 1756-PA75 power supply has a capacity of 13.0 amperes. I usually don't try to push the limits without having a good reason.

It sounds to me like you're trying to shoehorn a big function into a small package. You might want to get some advice directly on your application from your friendly local Rockwell Automation office.