Rockwell Automation 1785-LTx,D17856.2.1 Classic PLC-5 Programmable Controllers Users Manual - Manual (Page 80)

Planning Your System Programs
Chapter 6
6-9
Data Table Addressing Formats
Address Type Description Example
Logical address AlphaĆnumeric coded format to specify
the data location
N23:0 addresses an integer file 23, word 0
I/O image address Logical address format, but relates
physical locations in the I/O chassis to
memory locations in the I/O image file
I:017/17 addresses input file word 017 (octal), bit 17 (octal), which corresponds to
rack 01, module group 7, and terminal 17
Indirect address Logical address format, but allows you to
change address values in the base
address with your ladder logic program
N[N7:6]:0 has the file number as the variable
The file number is stored in integer file 7, word 6
Indexed address Index prefix (#) is followed by a logical
address format, but it adds an index
value (offset) from processor status file
to the base address
When #N23:0 is the indexed address and the offset value stored in the processor
status file is 10, then
• the base address is integer file 23, word 0
• and the offset address is integer file 23, word 10
Symbolic address ASCII character string that relates the
address (file, structure, word, or bit) to a
descriptive, meaningful name that you
assign
For example, a floating point address F10:0 could be given a symbolic address of
Calc_1. These symbols are a feature of the programming software and not of the
processor. Guidelines for setting up an address are as follows:
• Start the name with an alphabetic character.
• The symbol must begin with a letter and can have up to 10 of the following
characters: AĆZ (upper and lower case), 0Ć9, underscore (_) and @.
• You can substitute a symbolic address for structure, word, or bit addresses.
• Record the symbols you define and their corresponding logical addresses.
Use the Processor Status screen to monitor:
processor status information
major and minor faults
STIs
program scan times
I/O status
Processor status data is stored in status file S2. See Table 6.F.
Using the Processor
Status File