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

Page 206

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ASCII Module

PLC-2 Family Processors

Appendix A

AĆ38

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 A.16

Example Block Transfer Programming

WB001:0000

BTR

BLOCK XFER READ

RACK :

GROUP :

MODULE:

DATA :
LENGTH =

CNTL:

001

1 = HIGH

FI001:0005

FB001:0000

CNTL