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Modbus Communication Problem

Created by: Adham at: 6/15/2009 12:22 PM (4 Replies)

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6/15/2009 12:22 PM	Rate (0)
Adham Posts: 28 Rating: (0)	Hello All, I have a CP 341 with a CPU 315, i inserted the dongle in the CP 341 and loaded the drivers, the protocol i am using is the MODBUS MASTER, I have set up the communication pararmeters on the master, 9600 baud rate, etc.... and made the same settings on the slave. Then i connected the cable with the correct pin assignments " pins 4,8,11" and the shield is connected in the master side and in the slave side. But the CP 341 has no indication, the leds are all off, they only blink when the power is reset and then go off. The diagnostic buffer does not show any errors, PLEASE HELP ME. Adham
Adham Posts: 28 Rating: (0)
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6/15/2009 1:06 PM	Rate (0)
umencho Diamond Expert Joined: 3/21/2006 Last visit: 1/14/2025 Posts: 10239 Rating: (1182)	Hello Adham, - TXD (green) Send active; lights up when the CP 341 sends user data via the interface. - RXD (green) Receive active; lights up when the CP 341 receives user data via the interface. Perhaps manual could be helps: Entry-ID 1220184 Regards Hristo Mihalev

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6/15/2009 2:27 PM	Rate (0)
Adham Posts: 28 Rating: (0)	Hello UMENCHO, i have read the manual before and have done exactly the same steps, but still i have no TXD led or RXD led or even the SF led. i have tried 3 different CP 341 modules incase one of them was faulty. PLEASE HELP
Adham Posts: 28 Rating: (0)
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6/15/2009 2:56 PM	Rate (0)
daga Gold Member Joined: 3/18/2009 Last visit: 12/6/2024 Posts: 306 Rating: (94)	Are you getting any errors for your modbus block calls (FB7 and FB8)? Also, first try the sample program that gets installed with the Modbus PTP drivers. Try using a simulation software (likeModsim) to simulate your slave and see if you can get it to work.

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6/15/2009 3:07 PM	Rate (0)
Saravana kumar Gold Member Joined: 2/6/2009 Last visit: 1/7/2025 Posts: 939 Rating: (118)	Hi, I have faced the same problem once. My all settingswas ok. Finally I found that the "Modbus receive Block" FB7 was not called (enabled).Check the receive blockcall (Check in online). Please try to use the "CPUCLock Memory Byte" (1 sec pulse) togive the REQto the "Modbus Send Block" FB8 for testing purpose. The main thing is you have to give( 'X') this symbol at the "R_typ" of "Modbus Send Block" FB8 otherwise it wont work. Please find the attachment for the example of Modbus Block calls. Try the above options, if not working means let me know. Attachment Modbus Blocks Call.pdf (291 Downloads)
	_______________________________________________________________ Best Regards T.Saravana Kumar "All for the Best"
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