Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE - Manual (Page 149)

Function of Control/Status Bits
Chapter 6
6Ć14
Bit: SW1(04)
Function: Output Buffer Empty
Description: The module sets this bit when it detects that the output
buffer is empty. The module resets this bit when it detects that data
entered the output buffer.
Bit: SW1(05)
Functions: Output Buffer Full
Description: The module sets this bit when it detects that the output
buffer is full. The module resets this bit when the output buffer is less
than full.
Bit: SW1(06)
Function: Reserved for Future Enhancements
Description: The module sets this bit to zero.
Bit: SW1(07)
Function: Power-up Initialization
Description: The module sets this bit to show that the module has
undergone power-up initialization. Buffers have been cleared and
communication thru the module’s interface port has been turned off. This
bit must be reset by program logic in order to complete the power-up
initialization routine. This bit is reset by setting bit 07 of command word
one, CW1(07). When CW1(07) is set, bits 07, 15, and 16 of status word
one are reset. Then you can operate the module in default mode or
initialize the module to any other operating mode.
Bit: SW1(10)
Function: Data Complete
Description: The module sets this bit when it detects the end-of-string
delimiter in a transfer. When a long string of data is transferred over two
or more block transfers, the module sets this bit only in the last transfer
containing the end-of-string delimiter. For example, when a 300 character
string is transferred over three block transfers, the bit is not set until the
third transfer (Figure 5.1).