Rockwell Automation 1772-LS_LSP,D17726.8.6 PROG/OPER MANUAL-MINI PLC-2/05 - Manual (Page 40)

Memory Organization
Chapter 4
4Ć2
Figure 4.1
Word Address Equals Memory Bits
10248
Concept Example
Hardware Terminology Hardware Terminology
Input (1) or Output (0)
Rack No. (Always 1)
Module Group No.
(0-7)
Terminal No.
(00-07, 10-17)
Output: 0
Rack No.: 1
Module Group No.: 0
Terminal No.: 12
X X/XX X
Word
Data Table Terminology
Address
Bit
Address
0 0/12 1
Word
Address
Bit
Address
Data Table Terminology
Hardware vs Your Program
I/O terminal bit
module group word
module slot byte
one rack eight words
if the terminal has voltage (on state) a specific bit is on, which is a 1 in memory
if the terminal has no voltage (off state) a specific bit is off, which is a 0 in memory
To calculate the input and output image tables’ areas and how these values
compare with the hardware of your processor.
Remember: 1 rack = 8 words
You can only have one rack in this system.
Therefore: 8 words/rack x 16 bits - 128 I/O
Conclusion: The combined amount of usable bits in the input image
table and/or the output image table is 128 I/O.