Allen-Bradley 1747-ASB - 1;2-Slot Addressing Considerations

Publication 1747-UM006B-EN-P - June 2003
Addressing 3-11
1/2-Slot Addressing Considerations
When the 1747-ASB module is configured for 1/2-slot addressing, you
can use 4-, 8-, 16-, 32-point, discrete combination and specialty I/O
modules in any slot.
If the discrete mode is selected, specialty modules with four words or
less of input or output image are discretely mapped such as the
1746-NI4, -NO4I, -NO4V, and -HS. However, with a specialty module
such as the 1746-HS, the adjacent slot must be empty. Specialty
modules with more than four words of input or output image are
block transfer mapped such as the 1746-BAS.
If the block transfer mode is selected, all specialty modules are block
transfer mapped regardless of the image size.
The 1747-ASB module can block transfer map a maximum of eight
words.
With slot pairing, when a module is installed in slot 1 that requires all four
words of the input image, slot 1 uses the input image normally assigned to
slot 2. Slot 2, therefore, cannot use any of its input image. However, slot 2
can now use the output image normally assigned to slot 1, because slot 1
is not using it.
1514131211109876 5432 10
When a module is installed in slot 2 that requires all four words of the output
image, slot 2 uses the output image normally assigned to slot 1 (if slot 1 is
not already using it). The lesser slot number has priority over the greater.
Group 0
Slot 1
Group 1
Group 2
Group 3
1514131211109876 5432 10
Group 0
Slot 2
Group 1
Group 2
Group 3
Decimal
Octal701017
Decimal
Octal
701017
Slot 1
Paired
Slot 2
Paired
O
I = Input Module
= Output Module
I
O
I
O
Slot Pair
Input Image
Output Image
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