1747-6.22, Backup Scanner User Manual

7-120 RIO Block Transfer
Publication 1747-6.22
Control Flag
EN
TO
Status Flag
EW
ST
ER
DN
SLC Control Program Cancelling a Block Transfer Prior To
Transmission Across RIO Link
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M0 Control Information
M1 Status Information
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SLC Control Program Canceling a BT Prior to Transmission Across RIO
Link
In this example, the SLC control program cancels a BT that has been
pending (EW = 1, ST = 0) for a specific amount of time.
1. When the SLC control program detects that the EW has set, a
timer in the SLC control program starts.
2. If the timer expires before the scanner begins transmitting across
the RIO link (ST = 1), then the SLC control program sets the TO
flag. Note that the cancellation will not occur until all previously
scheduled BTs to the same logical rack have been completed
(i.e., when the ST bit would normally have been set).
3. The scanner fills in the error code field and sets the ER flag.
Also, the ER bit is not set until any previously pending BTs to
that device have been completed. The SLC control program must
clear the EN flag to complete the BT operation. Note that
because of the asynchronous nature of cancelling a device that
has a BT in progress, the BT reply may indicate either a
successful completion or an error.
4. 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.
5. Finally, the EW, ST (if set) and ER bits are reset.
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