Why Doesn't Total UM Add Up? - CX-Programmer

Sometimes the values shown on the CX-Programmer "Memory View" dialog do not seem to add up correctly, for example 5 + 4091 does NOT total 6144:

 

This is actually due to a more complex PLC algorithm than the dialog can display. In the example above, the PLC correctly has a maximum of 6144 words. This is shared between Program memory (which can have a maximim of 4096 words) and Comment memory (up to 5K words).

 

So this dialog correctly reports that the free UM for Program use is still 4091 words, and implies that there is still a minimum of 2053 words (6144 - 4091) left for Comment memory too. This simplifies the headline figure of available Program memory.