Rockwell Automation 1772-L8_LW_LWP_LX_LXP,D17726.5.8 User Manual - Manual (Page 277)

Block Transfer
Chapter 18
18-12
You can enter data directly into the block to be transferred. Position the
cursor over the block transfer instruction and press [Display] [1]. See
chapter 9.
Bi-directional block transfer is the sequential performance of both
operations. The order of operation is generally determined by the module.
Two data addresses must be used. In this example they are 030 and 031.
Both contain the module address. For bi-directional operation, each data
address word also contains an enable bit:
bit 16 for a Write operation (in 031)
bit 17 for a Read operation (in 030)
Important: These bits are automatically set by the Block Transfer Read
and Write instructions.
When the processor searches the data addresses in the timer/counter
accumulated area of the data table, it finds two consecutive data addresses
both containing the same module address. The read bit and the write bit
are set in two consecutive data addresses. When the processor finds a
match of the module address and the read or write enable bit (read bit or
write bit) for the desired direction of transfer, it then locates the file
addresses to which (or from which) the data will be transferred.
Figure 18.6 shows an example bi-directional block transfer.
BiĆDirectional Block Transfer