Omron CJ2 User Manual page 26

Caution
If a symbol or memory address (only symbols are allowed for ST program-
ming) is specified for the suffix of an array variable in ladder or ST program-
ming, be sure that the specified element number does not exceed the
maximum memory area range. For example, write the program so that pro-
cessing is executed only when the indirect specification is within the memory
area range by using a symbol comparison instructions or an IF statement.
Specifying an element number that exceeds the maximum range of the
memory area specified for the symbol will result accessing data in a different
memory area, and may result in unexpected operation.
If a symbol or address is specified for an offset in a ladder diagram, program
so that the memory area of the start address is not exceeded when the offset
is specified indirectly using a word address or symbol. For example, write the
program so that processing is executed only when the indirect specification
does not cause the final address to exceed the memory area by using an
input comparison instruction or other instruction.
If a indirect specification causes the address to exceed the area of the start
address, the system will access data in other area, and unexpected opera-
tion may occur.
20 CJ2 CPU Unit Hardware User's Manual