Rockwell Automation 1772-LV Mini-PLC - 2/15 Programmable Controller (Series B) Programming and Operations - Manual (Page 31)

Memory Organization
Chapter 4
4Ć2
Figure 4.1
Word Address Equals Memory Bits
10146-I
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
Instruction Address
0 0/12 1
Word
Address
Bit
Address
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 will be on and a 1 will be written in
memory
If the terminal has no voltage (off state) A specific bit will be off and a 0 will be written in
memory.
Now we will show you how to calculate the input and output image tables’
areas and how these values compare with the hardware of your system.
Remember: 1 rack - 8 words
You can only have one rack in this system.
Therefore: 8 words/rack x 16 bits - 128 I/O