The main functional difference between the 1756-L61 Series A and Series B is the way the battery works.
The Series B uses the 1756-BA2 batteries, with a new connector and a blue jacket. They are still 3.3V lithium cells but the new ones have a higher output for shorter periods of time.
Instead of having the controller RAM held up by the battery (as in all RA controllers in the past), the Series B controller runs the whole controller for a second or two after power loss and saves the current program and tag database to nonvolatile onboard storage (a chip, not the CF card). After the program and database are saved, the battery just maintains the realtime clock, which it can do for many months. Even if the battery dies or is removed, the nonvolatile memory will still load the program into RAM.
To fully clear a Series B controller you have to remove the battery and cycle power twice. That second power cycle doesn't have the battery to write the program to NVRAM so the NVRAM gets cleared.
The other changes to the Series B controller are physical: the CF card is accessible via the front instead of the bottom, the serial port is moved and recessed a little further. You can tell a Series B controller when it's in a chassis next to other modules because the main board and therefore the door hinge is a couple of millimeters lower in the front. Or, of course, open the door and you'll see the CF card slot and the blue battery jacket.
There is no difference in performance between a Series A and B 1756-L6x controller. The firmware is unaware of which Series of controller it's running in. Click Here To Order Controllogix Processor
The Series B uses the 1756-BA2 batteries, with a new connector and a blue jacket. They are still 3.3V lithium cells but the new ones have a higher output for shorter periods of time.
Instead of having the controller RAM held up by the battery (as in all RA controllers in the past), the Series B controller runs the whole controller for a second or two after power loss and saves the current program and tag database to nonvolatile onboard storage (a chip, not the CF card). After the program and database are saved, the battery just maintains the realtime clock, which it can do for many months. Even if the battery dies or is removed, the nonvolatile memory will still load the program into RAM.
To fully clear a Series B controller you have to remove the battery and cycle power twice. That second power cycle doesn't have the battery to write the program to NVRAM so the NVRAM gets cleared.
The other changes to the Series B controller are physical: the CF card is accessible via the front instead of the bottom, the serial port is moved and recessed a little further. You can tell a Series B controller when it's in a chassis next to other modules because the main board and therefore the door hinge is a couple of millimeters lower in the front. Or, of course, open the door and you'll see the CF card slot and the blue battery jacket.
There is no difference in performance between a Series A and B 1756-L6x controller. The firmware is unaware of which Series of controller it's running in. Click Here To Order Controllogix Processor
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