Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE - Manual (Page 152)

Function of Control/Status Bits
Chapter 6
6Ć17
When transferring multiple strings, the module will not split a string
between two block transfers, and the string length cannot exceed the
number of characters that can be transferred in 31 words. Two strings of
31 words, three strings of 20 words, and so forth, must total 62 words or
less. Remember that two of the 64 block transfer words are reserved for
status words. Do not confuse the transfer of multiple strings per block
with the transfer of one long string between two or more block transfers.
The module will split one long string between block transfers when you
have selected single string transfer, IW2(17)=0.
Command word one, status word one, and status word two are
summarized in Figure 5.2, Figure 5.3, and Figure 5.4, respectively.
Command, initialization and status words are summarized in the tables on
the following pages. Copy the figures and tables so that you can refer to
them as needed.
Figure 5.2
Command Word One, CW1
17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00
InitiaĆ
lizaĆ
tion
Write
Data
AvailĆ
able
Read
Data
AckĆ
nowĆ
ledge
Send
InĆ
comĆ
plete
String
Port
DisĆ
able
Self
DiagĆ
nosĆ
tics
0 Reset
Power
up and
Hand
shakĆ
ing Bit
0 Reset
Input
Buffer
Full
Bit
0 0