Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE - Manual (Page 154)

Function of Control/Status Bits
Chapter 6
6Ć19
Command Word One
Bit Function Status
17 Initialization 0 = Reset
1 = Up to four initialization words will follow
command words CW1 CW2
16 Write Data Available Toggled status, CW(16) ≠ SW(16), tells
module that transfer contains new data
15 Read Data Acknowledge Toggled status, CW(15) = SW(15), tells
module that processor received previous
transfer
14 Incomplete String 0 = Reset
1 = Used for installation debugging, not for
normal operation
13 Port Disable 0 = Reset
1 = Disables communication thru the interface
port
12 Self Diagnostics 0 = Reset
1 = Enables self diagnostics. You must reĆ
initialize the module
11, 10 Not used Set them to zero
07 Resets PowerĆup and
Handshaking
0 = Reset
1 = Resets SW1 (07) Initialization bit,
SW1(15) Read data available bit, and
SW1(16) Write data acknowledge bit
06, 05, 04 Not used Set them to zero
03 Resets Input Buffer
Full Bit
0 = Reset
1 = Resets SW1(03) buffer full
02 Not used Set it to zero
01 Reserved for future
use
Reset this bit to zero
00 Reserved for future
use
Reset this bit to zero