Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE - Manual (Page 148)

Function of Control/Status Bits
Chapter 6
6Ć13
Data Conversion
Internal
Fill Character
Displayed at a
Data Terminal as
3 BCD per word
4 BCD per word
4 Hex per word
00
00
00
0
0
0
1 ASCII per word
2 ASCII per word
20
20
blank
blank
Bit: IW4(17)
Function: Reserved for Future Enhancements
Description: Reset it to zero.
The first two words in every read block transfer are status words. Status
word one (SW1) reflects the module’s response to command word one.
Status word two (SW2) indicates the number of words and/or data blocks
transferred to the PC processor in each read block transfer.
Status Word One, SW1
Bit: SW1(00)
Function: Input Buffer Empty
Description: The module sets this bit (to 1) when it detects that the buffer
is empty. The module resets this bit when data enters the input buffer.
Bit: SW1(01)
Function: Input Buffer 50% Full
Description: The module sets this bit when it detects that the buffer is
50% full. The module resets this bit when the input buffer is less than
50% full.
Bit: SW1(02)
Function: Input Buffer 75% Full
Description: The module sets this bit when it detects that the buffer is
75% full. The module resets this bit when the input buffer is less than
75% full.
Bit: SW1(03)
Function: Input Buffer Full
Description: The module latches this bit (on) when it detects that the
buffer is full. It is reset by CW1(03) when the input buffer is empty.
Status Words