Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) - Manual (Page 299)

Chapter 15
Using Communication Protocols
15–15
Rung 2:2
Read message with preceding logic. It is STRONGLY recommended that bit
S2:0/11 (active protocol bit) be used to condition all message
instructions. This bit only allows the message instruction to operate
when the correct protocol is active. NOTE: If DF1 was the protocol used
by the message instruction, use –]/[– S2:0/11 for the preceding logic.
| DH-485 Active Read Message Ins. |
| S2:0 +MSG–––––––––––––––––––––+| |
|–––] [––––––––––––––––––––––––––––––+Read/Write Message +–(EN)+–|
| 11 |Read/Write Read+–(DN) |
| |Target Device 500CPU+–(ER) |
| |Control Block N7:60| |
| |Control Block Length 7| |
| | Setup Screen | |
| +––––––––––––––––––––––––+ |
Rung 2:3
This rung monitors the message instruction for “Done” conditions. When
the message is done, the enable bit is cleared allowing communication to
run again. The error retry bit is also used to reset the message if an
error or lockup condition is encountered.
| Read Message Read Message |
| Done Enabled |
| N7:60 N7:50 |
|–+––––] [––––––––––––––––+––––––––––––––––––––––––––––(U)––––––––––––|
| | 13 | 15 |
| | Message Error | |
| | Retry Timer | |
| | T4:9 | |
| +––––] [––––––––––––––––+ |
| DN |
Rung 2.4
| |
|–––––––––––––––––––––––––––––––––––––+END+–––––––––––––––––––––––––––|
| |