Allen-Bradley 1747-SN - Page 103

5–26 RIO Block Transfer
Publication 17476.6 - July 1996
Rung 2:1
COPY THE BTW STATUS AREA TO A BINARY FILE WHICH WILL BE USED THROUGHOUT THE
PROGRAM, ONLY WHEN A BTW IS PENDING. THIS AVOIDS ACCESSING THE M1 FILE MULTIPLE
TIMES DURING EACH PROGRAM SCAN. EACH TIME AN INSTRUCTION CONTAINING AN M1 FILE
BIT, WORD OR FILE IS SCANNED BY THE PROCESSOR,AN IMMEDIATE DATA TRANSFER TO
THE MODULE OCCURS AND THEREFORE WILL IMPACT THE PROCESSOR SCAN TIME.
| SERVICE |
| THE BTW |
| STATUS/ |
| BTW |
| PENDING BTW STATUS |
| B3:5 +COP–––––––––––––––+ |
|–+––––] [–––––+––––––––––––––––––––––––––––––––––––––––––+COPY FILE +–|
| | 0 | |Source #M1:1.100| |
| | | |Dest #B3:0| |
| | | |Length 4| |
| | | +––––––––––––––––––+ |
| | | |
| | CHECK BTW | |
| | STATUS | |
| | UNTIL DONE | |
| | BIT IS OFF | |
| | B3:5 | |
| +––––] [–––––+ |
| 1 |
Rung 2:2
UNLATCH THE BIT THAT CONTINUES TO CHECK THE BTW STATUS. WHEN A BTW IS
COMPLETE, THE DONE BIT IS SET. THE LADDER PROGRAM MUST THEN UNLATCH THE ENABLE
BIT, THEN WAIT FOR THE SN MODULE TO TURN OFF THE DONE BIT BEFORE ANOTHER BTW
TO THE SAME M–FILE LOCATION CAN BE INITIALIZED. THIS IS ONE COMPLETE BTW CYCLE.
| | |
| | CHECK BTW |
| VIRTUAL | STATUS |
| BTW DONE | UNTIL DONE |
| BIT | BIT IS OFF |
| B3:0 B3:5 |
|–+––––]/[–––––+–––––––––––––––––––––––––––––––––––––––––––––––––––––––(U)–––––|
| | 13 | 1 |
| | | |
| | VIRTUAL | |
| | BTW ERROR | |
| | BIT | |
| | B3:0 | |
| +––––]/[–––––+ |
| 12 |
Rung 2:3
WHEN A BTW SUCCESSFULLY COMPLETES, UNLATCH THE BTW ENABLE BIT. ALSO, UNLATCH
THE BTW PENDING BIT AND LATCH THE BIT THAT CONTINUES CHECKING THE BTW STATUS
UNTIL THE SN MODULE TURNS OFF THE DONE BIT.
| SERVICE |
| THE BTW |
| VIRTUAL STATUS/ |
| BTW DONE BTW |
| BIT PENDING |
| B3:0 B3:5 |
|––––] [––––––––––––––––––––––––––––––––––––––––––––––––––––––––+––––(U)–––––+–|
| 13 | 0 | |
| | | |
| | | |
| | VIRTUAL | |
| | BTW ENABLE | |
| | BIT | |
| | B3:100 | |
| +––––(U)–––––+ |
| | 15 | |
| | | |
| | CHECK BTW | |
| | STATUS | |
| | UNTIL DONE | |
| | BIT IS OFF | |
| | B3:5 | |
| +––––(L)–––––+ |
| 1 |