Point I/O Adapter Connection Limits
Sorry for the late reply. I read this the other day, but only got back to reply to it today...
the_msp said:
Looking to install a E/IP Point IO rack at maximum capacity... (63 modules)...
Personally, I'm with Ken on this one. I would not be too keen on adding the full complement of 63 modules to any Point I/O adapter when they can be possibly better segregated or indeed, where another platform might suit better - but if needs must, here are some further considerations...
The maximum of 63 modules for a Point I/O adapter is known as a "hard" limit. This basically means "...it is possible, but only if...". As well as power distribution and current draw considerations, you may also have connection limitations to consider here. The AENT has a limit of 5 "rack optimized connections" and 20 "direct connections". Only one of those 5 "rack optimized connections" can be an "owner" of the I/O modules i.e. can read/write to the modules.
It all depends on the bigger picture...
What mix of 63 I/O modules do you intend to add to the rack?
How many separate devices will need to communicate with the rack, or parts of the rack?
If more than one, then how many of them need to be an "owner" of unique I/O data within the rack?
If you were adding say, 63 digital I/O modules, then you could have one "rack optimized connection" from one "owner" controller to all 63 I/O modules. Similarly, up to four other "listen-only" controllers could use a "rack optimized connection" to the same 63 I/O modules. i.e. they can read the status of the 63 modules, but cannot write to them. This would be fine if you are only adding 63 digital I/O modules, and only looking to "own" the 63 modules from one controller.
As Point I/O is a distributed system, a user could be locating a lot of I/O together in one remote area, such as in the same enclosure, and then attempting to access parts of that I/O data from different controllers. If all placed in the same rack i.e. all under the same adapter, it may be possible that there are some modules, or groups of modules in that same rack, which will require a different "owner" to the other rack members.
If, for instance, 20 of 63 digital I/O modules require a unique "owner" who can read/write them, and the remainder of the modules require a different "owner" who can read/write them, then the first 20 would use up the one available "owner rack optimized connection" for the adapter. This means the remaining modules cannot be separately "owned" while residing under this same adapter. They would have to be placed in their own rack under another adapter. Or, one controller would have to own all 63 modules, and then indirectly use produced/consumed or messaging between other controllers that require ownership of some of the I/O data.
This adds complexity to the system, whereas splitting out ownership across separate Point I/O racks would simplify the setup. The trade-off is that you use more adapters, and it limits the number of modules per rack according to the ownership requirements.
Example layout...
63 digital I/O modules
A mix of 6 data users (Owner/Listen-Only)
All Point I/O to be installed in the same enclosure.
How many AENT(R) adapters will be required to segregate ownership?
1 Adapter = 5 rack optimized connections - 1 x Owner and 4 x Listen-Only, 20 direct connections
Owner = Controller that can read and write to modules under the same adapter in the same rack.
Listen-Only = Controller than can read I/O status only.
Controllers and their uniquely required access within the 63 modules:
Controller 1 = 07 Digital Input and 03 Digital Output modules (10 modules)
Controller 2 = 10 Digital Input modules (10 modules)
Controller 3 = 10 Digital Input modules (10 modules)
Controller 4 = 10 Digital Input modules (10 modules)
Controller 5 = 05 Digital Input and 05 Digital Output modules (10 modules)
Controller 6 = 04 Digital Input and 09 Digital Output modules (13 modules)
Controller 1 needs to write to Output modules, so it will require an owner connection. So it will use the one "owner rack optimized connection" available for the first adapter. This leaves 4 "listen-only rack optimized connections" free on the first adapter.
Controllers 2 - 4 do not need to write to any outputs, so they can use 3 of those 4 "listen-only rack optimized connections" available on the first adapter, leaving one free. So the modules for Controllers 2 - 4 can reside under the first adapter.
Controller 5 needs to write to Output modules, so it will require an owner connection. As the "owner rack optimized connection" is used on the first adapter, a second adapter must be used. This then leaves 4 "listen-only rack optimized connections" available on the second adapter.
Controller 6 also needs to write to Output modules, so it will also require an owner connection. So a third adapter must be used. Again, using the one "owner rack optimized connection" available to it, and leaving 4 "listen-only connections" free.
So 3 AENT(R) adapters are required to facilitate these 6 data users...
Adapter 1 = 40 Digital I/O modules (1 Owner/3 Listen-Only)
Adapter 2 = 10 Digital I/O modules (1 Owner)
Adapter 3 = 13 Digital I/O modules (1 Owner)
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If not all Digital I/O modules?
Analog and Speciality modules each use one of the 20 "direct connections" available per adapter. This limits you to 20 analog or speciality modules per rack.
Example layout...
63 mixed modules
A mix of 4 data users (Owner/Listen-Only)
All Point I/O to be installed in the same enclosure.
How many AENT(R) adapters will be required to segregate ownership?
1 Adapter = 5 rack optimized connections - 1 x Owner and 4 x Listen-Only, 20 direct connections
Owner = Controller that can read and write to modules under the same adapter in the same rack.
Listen-Only = Controller than can read I/O status only.
Controllers and their uniquely required access within the 63 modules:
Controller 1 = 13 Digital I/O modules, 02 Encoder modules (15 modules)
Controller 2 = 20 Analog I/O modules (20 modules)
Controller 3 = 20 Analog I/O modules (20 modules)
Controller 4 = 05 RTD modules, 03 Counter In modules (8 modules)
Controller 1 needs to write to Output modules, so it will require an owner connection. So it will use the one "owner rack optimized connection" available for the first adapter. Controller 1 also has 2 encoder modules, which will use a "direct connection" each, leaving 18 free.
Controller 2 uses 20 Analog I/O modules. Each will use one "direct connection". 18 of these could use the remaining 18 available on the first adapter. However, this would mean the last 2 would have to go to a new adapter, so a separate adapter, using all of its 20 "direct connections" would be preferable here.
Controller 3 also uses 20 Analog I/O modules, which will require 20 "direct connections", so another adapter would be required here, again, using all of its "direct connections".
Controller 4 uses 8 speciality modules - 05 RTD and 03 Counter In modules. Each of these uses a "direct connection", so another adapter would be required here, using 8 and leaving 12 "direct connections" free on the last adapter.
So 4 AENT(R) adapters are required to facilitate these 4 data users...
Adapter 1 = 15 Digital I/O modules (1 Owner)
Adapter 2 = 20 Analog I/O modules (1 Owner)
Adapter 3 = 20 Analog I/O modules (1 Owner)
Adapter 4 = 08 Speciality modules (1 Owner)
These are just a couple of examples of how a slightly more complex arrangement can end up limiting how many connections can be used through the adapter, and hence, the maximum number of modules permitted per adapter.
Even if the above does not relate in any way to your intended setup, it's still no harm to know these things going forward.
TBC...