Slc Control Program Canceling A Bt Once Transmitted Across Rio Link - Allen-Bradley 1747-SN User Manual

5–18 RIO Block Transfer
Publication 1747 6.6 - July 1996
SLC Control Program Cancelling a Block Transfer Once Transmitted Across RIO Link
Control Flag
EN
TO
Status Flag
EW
ST
ER
DN
SLC Control Program Canceling a BT Once Transmitted Across RIO
Link
This example illustrates an SLC control program cancelling a BT
operation.
In this example, the SLC control program wants a BT timeout
value less than the four second default value that the scanner uses.
When the SLC control program detects that the ST flag has set, a
timer in the SLC control program starts.
If the timer expires before the scanner returns a BT response (DN
or ER), then the program will set the TO flag.
 The scanner fills in the error code field and sets the ER flag. The
SLC control program must still clear the EN flag to complete the
BT operation. Note that because of the asynchronous nature of
cancelling a transmission to a device that has a BT in progress,
the BT reply may indicate either a successful completion or an
error.
 The SLC control program clears the TO and EN flags. Note that
if the SLC control program later attempts to initiate another BT
and the TO flag is still set, the scanner will ignore the BT
request.
 Finally, the EW, ST and ER bits are reset.
M0 Control Information

M1 Status Information