7/16/2009 12:39 PM | |
Joined: 11/26/2008 Last visit: 12/8/2023 Posts: 101 Rating: (4) |
Hello, I am trying to source/make a cable for connecting a Sentron PAC3200 to a CM1241 RS485 module for MODBUS RTU communications. I have attached the pages relating to the connections on the PAC RS485 adapterside of the cable. I would like to know the pin-out for the other side of the RS485 connecting to the CM1241 RS485 module. There are 3 connections... two signal and one ground. What pins should they be attached to on a 9 pin RS485 plug connector? Also if you have any information on modbus RTU communications in the S7-1200/PAC (that's not in the manual!) i would appreciate it. Thanks. AttachmentPAC cable.zip (1016 Downloads) |
9/24/2009 12:35 PM | |
Posts: 2 Rating: (0) |
To connect a PAC 3200 via RS485 MODBUS RTU you need 2-wire cable (3-wire with shield). For detailed explanation of the CM1241 please see the manual for S7-1200 on page 343. You can download the manual here: http://support.automation.siemens.com/WW/view/en/36932465 First you need to put a jumper between pin 6 (PWR) and 8 (TxD-) of the CM1241. This is necessary because for a 2-wire Modbus RTU communication you need a terminating resistor to manage sending and receiving of the telegrams. After you are done with the jumper connect pin 8 (TxD-) of the CM1241 with the -/A port of the PAC 3200 RS485 module. Then you need to connect pin 3 (TxD+) of the CM1241 with the +/B port of the PAC 3200 RS485 module. A connection between the GND pin of the CM1241 and the Com port of the RS485 module is optional. Now the communication between S7 and PAC 3200 should work. |
Last edited by: robingrosse at: 9/24/2009 12:37 PM |
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