Rockwell Automation 2706-LV2P_LV2R_LV4P_LV4R DL40 PLUS USER MANUAL - Manual (Page 103)

Remote I/O Communications 8–11
Publication 2706-6.1
DL40 Plus displays communicate with PLC controllers and Remote
I/O scanners and sub-scanners as if they were a Remote I/O rack.
The DL40 Plus is compatible with all Allen-Bradley scanners that
support Remote I/O. The DL40 contains all the necessary
electronics to connect directly to the Remote I/O cable linked to a
PLC, scanner, or sub-scanner.
A sub-scanner may be used with any PLC 5/15. It allows the PLC
5/15 to communicate with up to 7 logical racks and a maximum of
16 devices, or chassis, as they are commonly called. Scanners have
both physical and logical specifications:
Physical Specifications - The maximum number of separate Remote
I/O devices (such as I/O racks, drive systems, DL40s) the scanner
can communicate with.
Logical Specifications - The maximum number of racks the scanner
can address.
Note: Different scanners have different physical and logical
specifications. See the next page.
To configure the DL40 Plus with PLC controllers you need to know:
•
appropriate PLC or scanner module
•
amount of I/O the DL40 Plus uses for different applications
•
number of chassis (1771 I/O racks or DL40s) and the amount of
rack I/O addressing the scanner can accommodate
For Example
A typical valid Remote I/O configuration for PLC 5/15 would be:
(4) 1/4 racks, (2) 1/2 racks and (1) full rack
Total devices = 4 + 2 + 1 = 7 devices.
This configuration is within the physical specification of
12 for the PLC 5/15.
Note: PLC 5/15 Series B, Revision H or later have partial rack
addressing. Earlier versions were limited to full racks.
4 x 1/4 racks = 1 logical rack
2 x 1/2 racks = 1 logical rack
1 full rack = 1 logical rack
= 3 logical racks
This is within the 3- rack logical limitation of the PLC 5/15. An
invalid Remote I/O configuration for a PLC 5/15 would be (8) 1/2
racks. Although 8 is less than the 12 device physical specification,
(8) x 1/2
= 4 logical racks which is greater than the PLC 5/15’s 3
rack logical specification.
Physical vs. Logical
Addressing