Rockwell Automation 1771-IFE , D17716.5.90 USER MNL. ANALOG INPUT Module - Manual (Page 26)

Module Programming
Chapter 3
3-2
The PLC-2 program example regulates when each block transfer will be
initiated to eliminate problems caused by limited regulation of
bidirectional block transfers. Both storage bits are needed, as shown in the
example, to accomplish this task in all PLC-2 systems, local or remote,
with long or short program scans. Therefore, the program as shown is the
minimum required. Note that PLC-2 processors that do not have the block
transfer instruction must use the GET-GET block transfer format which is
outlined in Appendix E.
Figure 3.1
PLCĆ2 Family Sample Program Structure
Block Transfer Read
EN
[1] You can replace the pushbutton with a timer done" bit to initiate the block transfer
ENABLE
17
DN
DONE
15
Pushbutton [1]
L
Bit A
Done Bit Pushbutton [1]
U
Block Transfer Write
L
Done Bit
Storage
Block Transfer Write
Bit A
Done Bit
Storage
Bit B
Done Bit
Power-up
U
Block Transfer Read
Bit B Bit
Power-up
Bit
Storage BTR Done
EN
ENABLE
X7
DN
DONE
X7
Storage
Bit A Bit
Bit B
Power-up
Bit
Storage
EN
ENABLE
X6
DN
DONE
X6
Storage
Bit B
Bit A
write on a timed basis. You can also use any storage bit in memory.
1
2
3
4
5
6
7
BLOCK XFER READ
DATA ADDR:
MODULE ADDR:
BLOCK LENGTH:
FILE:
XXX
RGS
XX
YYYY - XXX
FILE TO FILE MOVE
COUNTER ADDR:
POSITION:
FILE LENGTH:
FILE A:
XXX
XXX
XXX
YYYY - XXXX
FILE R:
RATE PER SCAN
XXX - XXX
XXX
BLOCK XFER WRITE
DATA ADDR:
MODULE ADDR:
BLOCK LENGTH:
FILE:
XXX
RGS
XX
XXXX - XXXX
Storage
Storage
10954ĆI
Rung 1
Block transfer read buffer: the
fileĆtoĆfile move instruction holds the
block transfer read (BTR) data (file A)
until the processor checks the data
integrity. If the data was successfully
transferred, the processor energizes
the BTR done bit, initiating a data
transfer to the buffer (file R) for use in
the program.
If the data is corrupted during the BTR
operation, the BTR done bit is not
energized and data is not transferred to
the buffer file. In this case, the data in
the BTR file will be overwritten by data
from the next BTR.
Rungs 2 and 3
These rungs provide for a userĆinitiated
block transfer write (BTW) after the
module is initialized at powerĆup.
Pressing the pushbutton locks out BTR
operation and initiates a BTW that
reconfigures the module. Block transfer
writes will continue for as long as the
pushbutton remains closed.
Rungs 4 and 5
These rungs provide a readĆwriteĆread"
sequence to the module at powerĆup.
They also make sure that only one
block transfer (read or write) is enabled
during a particular program scan.
Rungs 6 and 7
These rungs are the conditioning block
transfer rungs. Include all the input
conditioning shown in the example
program.
BTR
BTW
PLCĆ2 Programming