Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE - Manual (Page 137)

Function of Control/Status Bits
Chapter 6
6Ć2
Description: Set this bit to reset the following status bits in status word
one:
Bit 07 Power-up initialization
Bit 15 Read data available
Bit 16 Write data acknowledge
Bit: CW1(10, 11)
Function: Reserved for Future Enhancements
Description: Reset it to zero.
Bit: CW1(12)
Function: Self Diagnostics
Description: Set this bit to enable the module’s self-diagnostic routine
which tests the module’s firmware, memory and timers. During the
self-diagnostic test, the module discontinues communication. After
completion, the module re-initializes itself to power-up default mode.
You must then re-initialize the module if you want it to operate in any
mode other than default.
Bit: CW1(13)
Function: Port Disable
Description: Set this bit to disable I/O communication thru the interface
port on the ASCII module. Otherwise, reset this bit to zero.
Bit: CW1(14)
Function: Incomplete String
Description: Set this bit to tell the module to transfer an incomplete string
in the next bock transfer. It allows you to examine the contents of the
input buffer. This command is intended for troubleshooting purposes.
Avoid using it during normal operation. Reset this bit to zero.
Bit: CW1(15)
Function: Read Data Acknowledge
Description: After the processor receives and processes new status and/or
data, the program toggles this bit. The toggled status, CW(15)=SW(15),
is returned to the module to acknowledge receipt.
Bit: CW1(16)
Function: Write Data Available
Description: Your program must toggle this bit to transfer data from the
ASCII module’s output buffer to the ASCII device. The toggled status,
CW(16)
=/
SW(16), accompanies the data. The program must receive
acknowledgment of the previous write block transfer, toggled status of