Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE - Manual (Page 135)

Handshaking
Chapter 5
5Ć6
A write (only) program requires only write handshaking. A read/write
program requires read and write handshaking.
The module can handle handshaking and data simultaneously. For
example, read block transfers could contain new data and
acknowledgment of the previous write block transfer.
Refer to “Complete Getting Started Program,” Appendix A for PLC-2
family and for PLC-3 controllers. Handshaking bits in the ASCII
module’s command and status words used in these programs are defined
as follows:
Word Bit Description
PLCĆ2
Address
PLCĆ3
Address
Command
Word 1
15
16
CW1(15)
CW1(16)
200/15
200/16
WD002:0000/15
WD002:0000/16
Status
Word 1
15
16
SW1(15)
SW1(16)
252/15
252/16
WD003:0000/15
WD003:0000/16
Choose program addresses that are compatible with your programming
needs.