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ModbusRTU error 16#8281

6/13/2019 12:35 PM	Rate (0)
wolka Bronze Member Joined: 3/26/2009 Last visit: 8/7/2025 Posts: 147 Rating: (0)	I have problem with Modbus RTU Communication. I use CPU 1516-3 PN/DP (firmaware 2.1.0) and CM PtP RS422/485 HF (firmaware 1.0). Baud:9600; Data bits: 8bits; Parity: none parity . Im trying to make master Modbus RTU Communication via RS485 Half duplex 2-wire operation in PLC with slave unit. The PORT parameter in Modbus_Comm_Load is correct : "Local~CM_PtP_RS422_485_HF" The modbus_master_rtu status go only: 7001- initialization, 7002 -transmission, 8281 - Negative aknowlage. The MODE parameter of Modbus_Comm_Load is 16#4, and the STATUS is 16#7082, and WRREC.Output.STATUS is 16#C080930 The are TXD RXd LEDs on communication module not blink. I don't understand - where is my error? Attachment MB master error.jpg (185 Downloads)

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6/13/2019 12:53 PM	Rate (0)
Kaulquappe Posts: 3093 Rating: (324)	Hello, probably this thread can help you. Regards, Kaulquappe
Kaulquappe Posts: 3093 Rating: (324)
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6/13/2019 3:12 PM	Rate (0)
wolka Bronze Member Joined: 3/26/2009 Last visit: 8/7/2025 Posts: 147 Rating: (0)	Kaulquappe Hello, probably this thread can help you. Regards, Kaulquappe Thanks, but replacing the versions didn't help. I tried combinations: Modbus_Comm_Load V3.0 - Modbus_Master B2.4 Modbus_Comm_Load V3.0 - Modbus_Master B2.2 Modbus_Comm_Load B2.0 - Modbus_Master B2.1 the result is error 16 # 8281

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