Rockwell Automation 1785-Lxxx Enhanced and Ethernet PLC-5 Programmable Controllers - Manual (Page 51)

Publication 1785-UM012D-EN-P - July 2005
Addressing I/O and Controller Memory 4-7
Addressing
Block-Transfer Modules Block-transfer modules occupy 8 bits in the controller’s I/O image table.
Since all block-transfer modules are bidirectional, they cannot be used to
complement either input or output modules.
Addressing Summary Use this table as a quick reference for addressing.
To Address Use
single slot modules assigned I/O rack and group number of the slot in which the
module resides and 0 for the module number
When using 1/2-slot addressing, use the assigned rack
number and the lowest group number and 0 for the module
number.
double-slot modules assigned rack number and the lowest group number and 0 for
the module number
Addressing
Mode
Guidelines
2-slot
•
Two I/O module slots = 1 group
•
Each physical 2-slot I/O group corresponds to one word (16 bits) in the input image table and
one word (16 bits) in the output image table
•
When you use 16-point I/O modules, you must install as a pair an input module and an output
module in an I/O group; if you use an input module in slot 0, you must use an output module in
slot 1 (or it must be empty). This configuration gives you the maximum use of I/O.
•
You cannot use a block-transfer module and a 16-point module in the same I/O group because
block-transfer modules use 8 bits in both the input and output table. Therefore, 8 bits of the
16-point module would conflict with the block-transfer module.
•
You cannot use 32-point I/O modules.
•
Assign one I/O rack number to eight I/O groups.
1-slot
•
One I/O module slot = 1 group
•
Each physical slot in the chassis corresponds to one word (16 bits) in the input image table and
one word (16 bits) in the output image table
•
When you use 32-point I/O modules, you must install as a pair an input module and an output
module in an even/odd pair of adjacent I/O group; if you use an input module in slot 0, you must
use an output module in slot 1 (or it must be empty). This configuration gives you the maximum
use of I/O.
•
Use any mix of 8- and 16-point I/O modules, block-transfer or intelligent modules in a single I/O
chassis. Using 8-point modules results in fewer total I/O.
•
Assign one I/O rack number to eight I/O groups.
1/2-slot
•
One half of an I/O module slot = 1 group
•
Each physical slot in the chassis corresponds to two words (32 bits) in the input image table
and two words (32 bits) in the output image table
•
Use any mix of 8-, 16-, and 32-point I/O or block-transfer and intelligent modules. Using 8-point
and 16-point I/O modules results in fewer total I/O.
•
With the controller-resident local rack set for 1/2-slot addressing, you cannot force the input
bits for the upper word of any slot that is empty or that has an 8-point or 16-point I/O module.
For example, if you have an 8-point or a 16-point I/O module in the first slot of your local rack
(words 0 and 1 of the I/O image table, 1/2-slot addressing), you cannot force the input bits for
word 1 (I:001) on or off.
•
Assign one I/O rack number to eight I/O groups.