Rockwell Automation 1791-XXXX ANALOG BLOCK I/O - Manual (Page 38)

Configuring Your Block I/O for PLC
Family Programmable Controllers
Chapter 3
3-5
When using block transfer, each analog block I/O module uses 2 words of
output image table memory and 2 words of input image table memory.
Each block occupies 1/4 rack of data table, with 4 blocks comprising 1
logical rack. Image table usage for one assigned rack number is shown in
Figure 3.3.
Figure 3.2
I/O Image Table for One Assigned Rack Number using Block Transfer
Output Image
Input Image
0
1
2
3
4
5
6
7
0 17
0
1
2
3
4
5
6
7
7 10
1791ĆN4C2
PLC
0 17 7 10 PLC
MSB
1/4 Rack
MCB
1/4 Rack
Block transfer requires 1/4 rack.
MSB = Module Status Byte
MCB = Module Control Byte
Reserved
Reserved
1791ĆN4C2
MCB
Reserved
1/4 Rack
1/4 Rack
MSB
Reserved