Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE User 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

BTR

BLOCK XFER READ

RACK :

GROUP :

MODULE:

DATA :
LENGTH =

CNTL:

001

1 = HIGH

FB001:0000

CNTL