Cascading expansion boards

[TTCSR]

I am using a FMD1616-10 with two EXP4040, however, the second expansion board is not operating.  The power light is on for both expansion boards and each works fine individually with the PLC, just not together.  

Is there something I need to do to the code to allow it to recognize the I/O beyond 40?

[support]

The expansion board should be plug-and-play and no software configuration is needed. However, do not hot-plug (i.e. when power is ON) or hot-unplug the expansion cable as it could potentially damage some electronics.

Since the expansion board works individually with the PLC, then it could be that the cascading port from the first expansion board is not working properly.

Did you try swapping the two boards and test it again? Assuming it is the cascading port from the first expansion board that is not working swapping the two board should work.

Also to eliminate any wrong software code that could have caused trouble, try loading a blank program into the PLC and then go online monitoring to remotely trigger the output on the second epansion board and manually turn on the physical inputs on the second expansion board and examine it on the monitoring screen. If the LED on the board correspond with that on the monitoring screen then the expansion boards are working properly.
 

[TTCSR]

I've tried a blank program and forcing outputs,  both expansions work.

I've tried a very simple program that turns on an output, both expansions work.

In my main program, the first expansion operational, but the second expansion still does not function.  I've even placed a line of code that simply turns on an output to the second board, and still nothing turns on, although the online monitioring screen shows the output as being on.  Really scratching my head on this one  

[TTCSR]

I have even tried deleting everything in my program and only leaving code that turns on an output for the second board.  It still doesn't work???  However, if I start a new program it does.  Is there something to reset the I/Os I don't know about?

[TTCSR]

Ok figured it out.  Once I reached output 40 in the program, the hardware skips the next 16 bits, so I can't use outputs 41 to 56, however, output 57 and up do work!  I guess the first 16 bits are reserved for a PLC's I/O even though the expansion is connected to another expansion?  

I wonder what happens to a PLC with less or more than 16?

At least I have it working with my program now  

[support]

The first EXP4040 occupies output 17 to 56 (40 inputs and 40 outputs, that's why it is called EXP4040). The first 24 I/Os are 24V NPN (i.e. input and output 17 to 40) and from I/O #41 to 56 they are TTL (5V logic) and are available on the header pins. You can turn on any input #41 to #56 by shorting the pin to its adjacent ground pin.