Publication 1747-UM013B-EN-P - January 2005
Block Transfer Examples for Earlier Processors D-21
Bidirectional Alternating Block Transfer
The following rungs demonstrate a bidirectional alternating block
transfer. Using these rungs ensures the block transfer requests are
executed in the order in which they are sent to the queue. This
example also ensures that the block transfer read and block transfer
write alternate. The XIO conditions prevent the BTR and BTW from
queueing simultaneously. The block transfers continue as long as the
XIC precondition bit is true.
Rung 2:12
MOVE THE VIRTUAL BTW CONTROL WORD TO THE M0 FILE FOR THE SN MODULE WHILE A BTW
IS IN PROGRESS, AND CONTINUE DOING SO UNTIL THE ENABLE, DONE AND ERROR BITS
ARE ALL TURNED OFF, COMPLETING THE HAND-SHAKE PROCESS.
| |
| |
| VIRTUAL BTW |
| BTW ENABLE CONTROL |
| BIT BITS |
| N7:53 +MOV---------------+ |
|-+----] [-----+------------------------------------------+MOVE +-|
| | 15 | |Source N7:53| |
| | | | 0| |
| | | |Dest M0:1.200| |
| | | | *| |
| | | +------------------+ |
| | | |
| | | |
| | VIRTUAL | |
| | BTW DONE | |
| | BIT | |
| | N7:64 | |
| +----] [-----+ |
| | 13 | |
| | | |
| | | |
| | VIRTUAL | |
| | BTW ERROR | |
| | BIT | |
| | N7:64 | |
| +----] [-----+ |
| 12 |
Rung 2:13
| |
|-------------------------------------+END+------------------------------------|
| |
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