Rockwell Automation 1203 Serial Communications Module Series B User Manual
Page 47
4–13
Configuring and Interfacing
1203–5.5 September 1995
DH–485 Messaging with a SLC5/03 Interface
The following example uses the DH–485 communications mode to
send a message from an SLC5/03 to the Serial Communications
Module.
Rung 2:0
If this is the first scan or the error bit is true, the MSG instruction’s control
byte is cleared and the done bit is set. This ensures that the program always
starts correctly and recovers from a MSG error.
| First |
| Scan |
| Bit |
| S:1 +AND–––––––––––––––+ |
|–+––––] [–––––+––––––––––––––––––––––––––––––––––––––+–+BITWISE AND +–+–|
| | 15 | | |Source A 255| | |
| | | | | | | |
| | | | |Source B N15:0| | |
| | | | | 8192| | |
| | | | |Dest N15:0| | |
| | | | | 8192| | |
| | | | +––––––––––––––––––+ | |
| | MSG Block | | MSG Block | |
| | Error (ER) | | Done (DN) | |
| | Bit | | Bit | |
| | N15:0 | | N15:0 | |
| +––––] [–––––+ +––––(L)–––––––––––––––+ |
| 12 13 |
Rung 2:1
When the MSG instruction is done, the TON provides a 2 second delay before another
message is sent. B3:0/0 represents user logic. The timer can be adjusted to
provide control over DH485 network loading.
| User |MSG Block |
| DH485 |Done (DN) |
| Enable |Bit |
| B3:0 N15:0 +TON–––––––––––––––+ |
|––––] [––––––––] [––––––––––––––––––––––––––––––––––+TIMER ON DELAY +–(EN)–|
| 0 13 |Timer T4:0+–(DN) |
| |Time Base 0.01| |
| |Preset 200| |
| |Accum 156| |
| +––––––––––––––––––+ |