Rockwell Automation 2711 PANELBUILDER SOFTWARE USER MANUAL - Manual (Page 366)

PLC Programming Considerations
Appendix A
A-2
Byte (slot)
This is also referred to as “slot” or “module”. Low byte (module or slot =
0) or high byte (module or slot = 1) of the assigned “module group (word)”
can be designated. This discrete byte address in the PLC input and output
image table will be used for block transfer control, and cannot be used by
other objects or functions.
Number of Words
The block transfer instruction in the PLC program will dictate the number
of read or write words (file size) to be transferred. If “zero” words are
entered in the block transfer instruction in the PLC program, then the
terminal will both read and/or write the number of words specified on the
PanelBuilder development system. A read or write file can be from 1–32
words.
For each block transfer assignment configured on the development system,
both a read and write file will be allocated in the terminal. Each PLC block
transfer instruction can access one read or write file in the terminal, as long
as the instruction’s rack number, module group and byte (slot) assignment
matches that of a block transfer assignment in the terminal.
If only read data, or only write data is to be transferred, then single
direction block transfers can be programmed in the PLC controller. To
transfer both read and write data, program the PLC controller for
bi-directional block transfer communication, as described in this section. In
this case block transfer read and write instructions in the PLC program
must both be assigned the same rack, module group and byte (slot), just
like bi-directional block transfers to an intelligent I/O module.
Remember that each block transfer assignment in the terminal supports
both a read and write block transfer file (32 words each). Do not make
additional block transfer assignments unless more than this is required.