Allen-Bradley PLC-5 User Manual page 56

4-12 Addressing I/O and Controller Memory
Publication 1785-UM012D-EN-P - July 2005
You might also want to leave room for future expansion
TIP
when grouping data. Do this by leaving gaps between:
data blocks within a file
groups of sequentially numbered files
modules in an I/O chassis
If you plan to edit your program online in Run mode, you
IMPORTANT
must allocate unused data table files/elements and program
files because you cannot create user memory while in run
mode. Each unused file, however, uses 6 words of overhead
memory for each data/program file you skip. Use care
when leaving gaps.
Follow these guidelines when organizing data files:
TIP
Group large amounts of related data into files.
Address the data files from 3-999 as needed.
(See on page page 13).
Address the words needed in each data file
consecutively from 0-999 (0-1999 for some data types
in series E, revision D controllers and later).
Address the words of I/O image data according to how
you configured your I/O:
– 0-37 (octal) for PLC-5/11, -5/20, -5/20E
– 0-77 (octal) for PLC-5/30
– 0-177 (octal) for PLC-5/40, -5/40L, -5/40E
– 0-277 (octal) for PLC-5/60, -5/60L, -5/80, -5/80E
When addressing I/O image bits, address them 00-07
or 10-17 (octal).
When organizing bit data, address the bits in each word
0-15 (decimal) for binary or integer files.
Each data table file allocates 6 words of memory when you
create the file. This is in addition to any data stored in the
file.