https://forge.codesys.com/forge/talk/Engineering/thread/7f859f63b5/2022-04-27T07:16:00.561000ZRecent posts to Codesys 3.5 Modbus TCP Slave illegal data address2022-04-27T07:16:00.561000Z2022-04-27T07:16:00.561000ZdFxhttps://forge.codesys.com/u/dfx/https://forge.codesys.com635a2a9ec5e9ef9341c8ae2a0af8b2ebef491ef8

<div class="markdown_content"><p>Unit ID feels wrong also, even if it seems to work.<br/> Recall that serial Modbus uses addresses 1 to 247 decimal, and reserves 0 as a broadcast address.</p> <p>Even if some modbus TCP devices just ignore the address and echoes it back, 255 is generally used for a single device.<br/> So if this device is a gateway, 1-247 is generally used with a gateway(TCP/SL) to point a device on SL.</p> <p>Exception <br/> <em> Code MODBUS name Comments <br/> </em> 01 - Illegal Function Code - The function code is unknown by the server <br/> <em> 02 - Illegal Data Address - Dependant on the request <br/> </em> 03 - Illegal Data Value - Dependant on the request <br/> <em> 04 - Server Failure - The server failed during the execution <br/> </em> 05 - Acknowledge - The server accepted the service invocation but the service requires a relatively long time to execute. The server therefore returns only an acknowledgement of the service invocation receipt. <br/> <em> 06 Server Busy - The server was unable to accept the MB Request PDU. The client application has the responsibility of deciding if and when to re-send the request. <br/> </em> 0A Gateway problem - Gateway paths not available. <br/> * 0B Gateway problem - The targeted device failed to respond. The gateway generates this exception.</p></div>

2022-04-26T11:59:15.353000Z2022-04-26T11:59:15.353000Ztimvhhttps://forge.codesys.com/u/timvh/https://forge.codesys.com195e9a3cfc35edc740acfc20ac74ebc1bbd72adf

<div class="markdown_content"><p>Keep in mind that Modbus starts with address 1, but this is actually register 0. CODESYS uses a 0 based offset. So what you can try is to read 3200, because maybe your device uses a 1 based offset.</p> <p>Additionally maybe you can set the length to only one register just to see if this works.</p></div>

2022-04-14T09:35:28.462000Z2022-04-14T09:35:28.462000Zgerberhttps://forge.codesys.com/u/gerber/https://forge.codesys.comee40997c6bff72e36f3b5257afc38ab7c41df200

<div class="markdown_content"><p>Hi,</p> <p>I’m trying to establisch communicate with a Modbus TCP slave.<br/> I need to reed address 3201 by using FC3. For some reason I always get error “illegal data address”.<br/> I have double checked the addressing (Unit ID = 0, FC3, offset 3201) with an external Modbus TCP tool and this works. </p> <p>Do I miss something within the Codesys configuration</p></div>