Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual - Manual (Page 197)

Block Transfer
Chapter 10
10Ć14
2. Block Transfer will be enabled during the program scan. The transfer
will be performed during an interruption of the next I/O scan. Data
from the module will be loaded into words 050-052. When block
transfer is complete, done bit 114/07 is set in the input image
table byte. This indicates that the block transfer was successfully
performed. The processor then continues with the I/O scan and
program scan.
3. During the program scan, rung 1 will be true because bit 010/00 is
still latched on and bit 114/07 (the block transfer done bit) is on
because block transfer was performed. This will turn bit 010/02 on.
In rung 2, bit 010/00 is then unlatched.
4. In rung 5, bit 010/02 is still on and a diagnostic bit is examined to
ensure the data read from the module is valid. Assuming the data is
valid, the diagnostic bit will be on and the data will be transferred
from word 050 to 150. In rungs 6 and 7, the data in words 051 and
052 will be transferred to words 151 and 152 if the diagnostic bit is
on.
Bidirectional block transfer is the sequential performance of both
operations. The order of operation is generally determined by the module.
Two rungs of user program are required, one containing the block transfer
read instruction, the other containing the block transfer write instruction.
When both instructions are given the same module address, the pair are
considered as bidirectional block transfer instructions. See Figure 10.3 for
block transfer format and definitions.
The operation of bidirectional block transfer is similar to that described in
section 10.1, basic operation. Additional considerations for bidirectional
operation will be described using an example read and write instruction
with equal block lengths having the following parameters:
Read instruction
Data address 040
Module address 130
Block length 05
File 070-074
Write instruction
Data address 041
Module address 130
Block length 05
File 060-064
10.9
Bidirectional Block Transfer
10.9.1
Operation