Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE - Manual (Page 150)

Function of Control/Status Bits
Chapter 6
6Ć15
Figure 5.1
Operation of Data Complete Bit
Block Transfer Data Status of SW1(10)
BT1 containing SW1, SW2, and first 124 characters
BT2 containing SW1, SW2, and second 124 characters
BT3 containing SW1, SW2, and remaining characters*
SW1(10)=0
SW1(10)=0
SW1(10)=1
*with end of string delimiter BT=block transfer
The module also sets this bit when it transfers a string equal to the set
string length when the input string exceeds maximum, SW1(14)=1.
Bit: SW1(11)
Function: Reserved for Future Enhancements
Description: The module sets this bit to zero.
Bit: SW1(12)
Function: Initialization Error
Description: The module sets this bit and ceases to operate when it
detects an error in your initialization data. For example, the same
character has been selected for delimiter and fill character. It is reset
when the module receives valid initialization data. Refer to Initialization
Errors, Table 6.A, for a complete list of settings that cause an initialization
error.
Bit: SW1(13)
Function: ASCII Device or Link Error
Description: The module sets this bit when it detects a parity, framing, or
overrun error in the string of characters from the ASCII device. When
multiple strings are transferred in one read block transfer, program logic
can detect the error but cannot detect which string(s) contained the error.
The module resets this bit when it detects no errors.
Bit: SW1(14)
Function: Input String Exceeds Maximum
Description: The module sets this bit when it detects an input string
longer than the string length that you selected in IW2(00-13). The
module transfers the number of characters equal to the set string length.
The remaining string characters (spillover) are stored in the module’s
input buffer as the first data of the next string. If the spillover was
terminated by an end-of-string delimiter, the module would transfer it as
another string. If not terminated by a delimiter, subsequent data strings
could be out of sequence. The bit is reset when the module processes a
string without spillover.