Rockwell Automation 1785-Lxxx Enhanced and Ethernet PLC-5 Programmable Controllers - Manual (Page 63)

Publication 1785-UM012D-EN-P - July 2005
Addressing I/O and Controller Memory 4-19
When you specify indirect addresses, follow these guidelines:
• You can indirectly address the file number, word number, or bit number.
• The substitute address must be one of the following types: N, T, C, R,
B, I, O, or S. Any T, C, or R address must be a word-length sub-member
address, such as T4:0.ACC.
• Enter the pointer address in brackets [ ].
For example, if you enter O:[N7:0] and N7:0 contains the value 10, the value at
N7:0 is converted to octal and the resulting address is O:012, not O:010.
To monitor for invalid indirect addresses, condition the rung with the indirect
address with a limit test of the indirect address to ensure that the address stays
within the intended range. This is especially advisable if the PLC-5 controller
has no control over the indirect address, such as the value is determined by
values from an I/O module or a peer controller.
Example Variable Explanation
N[N7:0]:0 File number The file number is stored in integer address
N7:0.
N7:[C5:7.ACC] Structure number The word number is the accumulated value
of counter 7 in file 5.
B3/[I:017] Bit number The bit number is stored in input word 17.
N[N7:0]:[N9:1] File and word number The file number is stored in integer address
N7:0 and the word number in integer
address N9:1.
ATTENTION
If you indirectly address the input or output image table,
the value you specify in the integer file that you use for the
indirection (the pointer) is converted to octal when
executed by the instruction.