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I am trying to establish two RS485 Modbus communications between Siemens (417-H CPU) and Yokogawa DCS (ALR121) which can take up to 2 connections. Siemens side 2 CPUs and Yokogawa side one card and each connection is by 2 wire. In fact Siemens side with identical logic and with different machine.
What I am witnessing is: if I test individual connection (one connection to ALR121), both communications are fine. Within 1-2 sec signal reach each other. Whereas when I make full connections (two connections to ALR121), there is 5~10 sec signal delay and even some signal get lost.
Each connection has same address scheme with different slave ID. Connection parameter used is parity=None, data bit=8, speed=19200. CPU loading of DCS side is lower than 40 %.
Can someone tell me about the maximum data one ALR121 card can take? Or something about cyclic update mode? What other parameter can I think of?
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What I am witnessing is: if I test individual connection (one connection to ALR121), both communications are fine. Within 1-2 sec signal reach each other. Whereas when I make full connections (two connections to ALR121), there is 5~10 sec signal delay and even some signal get lost.
Each connection has same address scheme with different slave ID. Connection parameter used is parity=None, data bit=8, speed=19200. CPU loading of DCS side is lower than 40 %.
Can someone tell me about the maximum data one ALR121 card can take? Or something about cyclic update mode? What other parameter can I think of?
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