Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE - Manual (Page 235)

ASCII Module
For PLCĆ3 Proessor
Appendix B
B-13
Program the read and write block transfer instructions of your
ASCII module in the same rung (Figure A.16).
Distribute your block transfer modules equally between all four
scanner channels.
Distribute block transfer instructions equally throughout your
program. Place an equal number of non-block transfer rungs
between block transfer rungs.
For large numbers of block transfer instructions, distribute groups
of block transfer rungs equally throughout your program. Place no
more than four block transfer rungs consecutively in one group.
Within each group, condition the next rung using the done bit of
the previous block transfer instruction.
Consider an additional I/O scanner module (cat. no. 1775-S4A) if
you cannot otherwise reduce the block transfer times to meet your
timing requirements.
During a write handshake, the processor also can transfer write
data to the ASCII module; and during a read handshake, the
processor also can transfer read data.
Figure B.7
Example Block Transfer Programming
WB001:0000
15
WB001:0000
05
BTR
BLOCK XFER READ
RACK :
GROUP :
MODULE:
DATA :
LENGTH =
CNTL:
001
1
1 = HIGH
F
0
FB001:0000
CNTL
12
EN
CNTL
15
DN
CNTL
13
ER
WB001:0000
17
BTW
BLOCK XFER WRITE
RACK :
GROUP :
MODULE:
DATA :
LENGTH =
CNTL:
001
1
1 = HIGH
FO001:0004
0
FB001:0000
CNTL
02
EN
CNTL
05
DN
CNTL
03
ER
I
001:0005