1747-asb module 2 i/o mapping details -22 – Rockwell Automation 1747-ASB Remote I/O Adapter User Manual

Page 126

Publication 1747-UM006B-EN-P - June 2003

8-22 Application Examples

1747-ASB Module 2 I/O Mapping Details

Because 1747-ASB module 2 is configured for 1/2-slot addressing, has
six logical groups and three slots available for I/O, all of the slots
present are mapped into the PLC-5/40 image. Since slot three cannot
be paired with slot four and only two words of image are available,
slot three has the two words assigned to it.

1747-ASB module 2 is configured for discrete mode operation.
Therefore, all speciality modules that have four or less words of input
and output image are discretely mapped, while all specialty modules
that have more than four words of input image or output image are
block transfer mapped.

Due to slot pairing, a discretely mapped four word analog input and
output module are allowed in one slot pair. The 1746-NI4 module in
slot one uses the four input words assigned to slots one and two. As a
result, slot two cannot use any input image. Conversely, it can use the
four output image words assigned to slots one and two which then
allows the 1746-NO4I output module to be installed in slot two.

Because slot three has two input and output words assigned to it and
the 1746-NIO4I module in slot three requires two input and output
words, the 1746-NIO4I module can be installed in slot three. If a four
word input or output module is installed in slot three, a 1747-ASB
module error occurs because only half of the module's image can be
mapped.

PLC Processor Input Image

PLC Processor Output Image

Bit Number

Octal

Bit Number

Octal

Logical

Rack 3

I:030
I:031
I:032
I:033
I:034
I:035

Group 0
Group 1
Group 2
Group 3
Group 4
Group 5

Logical

Rack 3

O:030
O:031
O:032
O:033
O:034
O:035

Group 0
Group 1
Group 2
Group 3
Group 4
Group 5

1747-ASB
Module 2

NO4I

NIO4I

1747-ASB
Module 2

NIO4I

NI4

ASB 2

1746

–NI4

1746

–NO4I

1746

–NIO4I

Group 2,3

Group 4,5

Group 0,1