Allen-Bradley 1771-ASB - Complementary I;O with 2-Slot Addressing

Chapter 3
Addressing Modes for Your Remote I/O
3-9
Some processors support a complementary I/O configuration. Refer to the
user manual for your processor to see if it supports this type of
configuration.
You configure complementary I/O by duplicating an I/O rack number of
one I/O chassis (primary) in another I/O chassis (complementary), I/O
group for I/O group. The I/O modules in the complementary chassis
perform the opposite function of the corresponding modules in the primary
chassis.
With 2-slot addressing you install, as a pair, the same type of 8-point I/O
module in an I/O group of the primary chassis. You install, as a pair, the
opposite type of 8-point I/O module in the corresponding I/O group of the
complimentary chassis.
For example, with an I/O chassis set for 2-slot addressing, place two
8-point input modules in I/O group 0 of the primary chassis. In I/O group 0
of the complementary chassis, place two 8-point output modules
(Figure 3.8). Use the same type of 8-point I/O modules in both slots of a
single I/O group.
Figure 3.8
Example
of Complementary I/O Configuration with 2slot Addressing
I
O
I
O
O
I
BT
BT
BT
Double-slot
BT
Double-slot
BT
E
M
P
T
Y
E
M
P
T
Y
E
M
P
T
Y
E
M
P
T
Y
E
M
P
T
Y
E
M
P
T
Y
E
M
P
T
Y
021 34567
O
021 34567
Example A
Example B
Primary 16-slot
Chassis
I/O G roup
Number
Complementary
16-slot Chassis
Primary 16-slot
Chassis
I/O G roup
Number
Complementary
Chassis Not
A llo w e d
Except for Output
I = Input Module
O = Output Module
BT = Block transfer Module
1 Output modules use the same output image table bits
2 Can be 8-point input or output module or single-slot block transfer module
3 Must be empty if corresponding primary slot is block transfer module
2
13
13079
Outputs in the complementary chassis use the same bits in the output image table as
the outputs in the primary chassis.
3
3
333
8
I
8
8
O
8
16
16
O
8
O
8
8
8
O
8
O
8
O
8
I
8
I
8
O
8
O
8
O
8
O
8
O
8
I
16
16
I
16
O
16
I
16
I
16
I
16
I
16
I
16
I
16
O
16
O
16
O
16
O
16
O
16
O
16
Complementary I/O with
2Slot Addressing
Allen-Bradley PLCs