Post by timvh on JSON ^{CODESYS Forge talk (Post)}
I don't know the details of jsonArrayWriter, but the common behaviour for an xExecute input is that the FB starts on the trigger that it gets TRUE. In your case xExecute is never FALSE, so it is never triggered again to start the jsonArrayWriter. So change the condition from TRUE to a variable which you set to TRUE with the "xFirst". Then when the jsonArrayWriter is done (xDone), or has an error (xError), then set this variable to FALSE.
Last updated: 2024-05-01

Post by culius on Official MQTT-Client: MAX_RECEIVE_BUFFER_SIZE_EXCEEDED ^{CODESYS Forge talk (Post)}
Thank you very much for your reply. That helped, it is editable if the library is at root level. Unfortunately, I noticed that I am not using the MQTT client SL, but the AzureMQTTClient from the Azure IoT Hub Client SL library. At first glance, there is no parameter to increase the message size. Does anyone know how to increase this in the library or is it simply not possible here?
Last updated: 2024-06-08

Post by nano on How to access to variable value through symbolic string name ^{CODESYS Forge talk (Post)}
i know, this is the reason for us either. PLC-Handler is to big, and only available with additional Contracts/Costs. OPC-UA is to slow for us. As described, there is a solution available, but im not allowed to post them here. i would prefer you send a message at codesys store by "have a question" or similar called. Not sure. Or, if an Codesys-Official Member allows to share that informations, i can give you the right hints.
Last updated: 2024-06-15

Post by mos89p on No Visu on RasPi ^{CODESYS Forge talk (Post)}
hi dialog is shown see attached picture
Last updated: 2024-06-20

Post by eschwellinger on SysProcessExecuteCommand2 and CANopen Device ^{CODESYS Forge talk (Post)}
which runtime version is it? 4.11.0.0?
Last updated: 2024-06-21

Post by mg0815 on ERROR: Calling the program "AlarmStorage_Prg" is not allowed from multiple tasks ^{CODESYS Forge talk (Post)}
...
Last updated: 2025-11-04

Post by kalmeyer on Stepper motor control with (SM_Drive_RaspStepper_direct) ^{CODESYS Forge talk (Post)}
HERE IS MY PLC_PRG /KLAUS
Last updated: 2025-11-04

Post by eschwellinger on Stepper motor control with (SM_Drive_RaspStepper_direct) ^{CODESYS Forge talk (Post)}
Which SoftMotion version is installed?
Last updated: 2025-11-06

Post by timvh on Deploy Codesys Control SL to a 'secure' device ^{CODESYS Forge talk (Post)}
Runtime version SP22 is an LTS version.
Last updated: 6 days ago

Post by dgross on Alarm Manager History Message Missing ^{CODESYS Forge talk (Post)}
Hi All, I'm using a webvisu on a control Win V3 SoftPLC. My issue is with the Alarm Managers Alarm history. It does create entry's and does also show the latch data. But it only shows the message of the active alarms. In the history the message is empty (also in the .csv Export file). The archiving in the alarm group is checked and the Alarm storage is activated. I'm using the Version V3.5 SP22 Patch 1. Do you have any idea where that comes from?
Last updated: 2026-04-20

Post by swol on Font Underline on webvisu not shown ^{CODESYS Forge talk (Post)}
Over 5 years later - is this still current information?
Last updated: 2026-01-29

Post by mrkm-dic on CODESYS: Combining Master Redundancy with EtherCAT Ring Topology – Is it Supported? ^{CODESYS Forge talk (Post)}
Hello, I would like to ask whether it is technically supported (and practically achievable) to combine CODESYS Master Redundancy with EtherCAT ring (loop) redundancy in the same system. System setup CODESYS version: CODESYS 3.5.21.40 CODESYS Control SL for Weidmuller u-OS-4.12.2.0 Controllers (Masters): Weidmuller UC20-M4000 ×2, configured as Active / Standby using CODESYS redundancy EtherCAT Slaves: Weidmuller UR20-FBC-EC ×3, supporting EtherCAT ring / line break detection Topology: EtherCAT ring (loop) Main question Is it officially supported to use: ・CODESYS PLC/Master redundancy (Active/Standby) and ・EtherCAT ring topology (for cable redundancy) at the same time? Expected behavior Our expectation is: ・When the Active PLC fails, the Standby PLC becomes Active ・The Standby PLC then takes over the role of EtherCAT Master ・EtherCAT communication is re-established ・I/O control continues after reinitialization (a short interruption is acceptable; no strict bumpless requirement) We do not expect completely seamless / zero-cycle switchover, but we want to understand: ・Whether this combination is supported by design ・Or whether there are known limitations or restrictions when EtherCAT ring mode is used together with Master redundancy Clarification At this stage, the question is mainly about feasibility and support, not about a specific error message yet. Any official guidance, limitations, or real-world experience would be greatly appreciated. Thank you in advance.
Last updated: 2026-02-05

Post by ilya-vah on Table element issues ^{CODESYS Forge talk (Post)}
Hello, First post here. I would like to clarify whether the following behavior is known or if it is a bugs. Issue 1 — First row not displayed when using Maximum array index with 1-based arrays Description: When displaying data from an array that is indexed starting from 1 (e.g., ARRAY[1..N]), and the number of displayed rows is limited using the Maximum array index property, the first row of the array is not shown in the visualization. Steps to reproduce: Create an array indexed from 1 (e.g., ARRAY[1..N]). Bind the array to a Table element. Limit the number of displayed rows using the Maximum array index property. Run the visualization. Actual result: The first array element (index 1) is not displayed in the table. Issue 2 — Tooltip string placeholder cannot be bound to string variable from array Description: It is not possible to use a string placeholder in the tooltip that is bound to a string variable from the array. Steps to reproduce: Use a table bound to an array containing string variables. Configure a tooltip using a string placeholder referencing a string field from the array. Run the visualization. Actual result: Tooltip doesn't show any text. A test project demonstrating both issues is attached. Thank you for your time and support.
Last updated: 2026-02-16

Post by nicolasquintin on Codesys Installation Always Freeze when the installing is almost done ^{CODESYS Forge talk (Post)}
Indeed that worked, thanks!
Last updated: 2026-04-05

Post by confre on Combo box drop-down invisible ^{CODESYS Forge talk (Post)}
Hi, I created a combo box and I need to know when the drop‑down menu is open, in order to avoid hiding the combo box while the drop‑down is visible. Alternatively, if it’s not possible to detect whether the drop‑down is open, I would like to know how to close or hide the drop‑down programmatically when the combo box is made invisible. I'm using Codesys 3.5 SP19 on IFM CR1074 without touch screen (with standard keyboard handling) Thanks.
Last updated: 2026-04-09

Post by totorovic on Ladder editor bug with 3.5.21.20 ^{CODESYS Forge talk (Post)}
Ladder version is 1.1.0.0
Last updated: 2026-05-28

Post by yannickasselin on Beckhoff CX9240 : Using Internal EtherCAT Bus ^{CODESYS Forge talk (Post)}
Control RTE is for Windows. @arj3090 specified Linux.
Last updated: 2026-07-10

Post by mondinmr on Direct Pointers in IOMapping for EtherCAT with IoDrvEthercatLib.ETCSlave_Dia ^{CODESYS Forge talk (Post)}
I have found a very interesting solution using: IoConfigTaskMap IoConfigConnectorMap IoConfigChannelMap The first is the list of IO tasks. The second is the connector for each IO module in the IOMap. The third is the individual input or output on the IOMap. One of the properties of the connector is another pointer to a connector, which corresponds with the connector of the EtherCAT slave. Through this information, it is possible to understand to which EtherCAT slave an IO connectormap corresponds. I am attaching an FB that allows for the construction of an IO map and finding the pointer to the actual IOs in the IOMap based on the bitoffset. FUNCTION_BLOCK IOExplorer VAR_INPUT END_VAR VAR_OUTPUT END_VAR VAR inputChannels: COL.LinkedList; outputChannels: COL.LinkedList; ulintFactory: COL.UlintElementFactory; END_VAR METHOD inputAtBitOffsetOfConnector : POINTER TO BYTE VAR_INPUT conn: POINTER TO IoConfigConnectorMap; bitOffset: UDINT; END_VAR VAR it: COL.LinkedListIterator; itf: COL.IElement; elem: COL.iUlintElement; channelInfo: POINTER TO ADVChannelInfo; bitOffsetR: UDINT; END_VAR inputChannels.ElementIterator(it); WHILE it.HasNext() DO it.Next(itfElement => itf); __QUERYINTERFACE(itf, elem); {warning disable C0033} channelInfo := TO___UXINT(elem.UlintValue); {warning restire C0033} IF channelInfo^.connectorField = conn THEN IF bitOffsetR = bitOffset THEN inputAtBitOffsetOfConnector := channelInfo^.addr; RETURN; END_IF bitOffsetR := bitOffsetR + channelInfo^.size; ELSE bitOffsetR := 0; END_IF END_WHILE inputAtBitOffsetOfConnector := 0; END_METHOD METHOD outputAtBitOffsetOfConnector : POINTER TO BYTE VAR_INPUT conn: POINTER TO IoConfigConnectorMap; bitOffset: UDINT; END_VAR VAR it: COL.LinkedListIterator; itf: COL.IElement; elem: COL.iUlintElement; channelInfo: POINTER TO ADVChannelInfo; bitOffsetR: UDINT; END_VAR outputChannels.ElementIterator(it); WHILE it.HasNext() DO it.Next(itfElement => itf); __QUERYINTERFACE(itf, elem); {warning disable C0033} channelInfo := TO___UXINT(elem.UlintValue); {warning restire C0033} IF channelInfo^.connectorField = conn THEN IF bitOffsetR = bitOffset THEN outputAtBitOffsetOfConnector := channelInfo^.addr; RETURN; END_IF bitOffsetR := bitOffsetR + channelInfo^.size; ELSE bitOffsetR := 0; END_IF END_WHILE outputAtBitOffsetOfConnector := 0; END_METHOD METHOD scanIO VAR_INPUT END_VAR VAR numTasks: DINT := IoConfig_Globals.nIoConfigTaskMapCount; tType: WORD; ioTask: POINTER TO IoConfigTaskMap; numCon: WORD; connector: POINTER TO IoConfigConnectorMap; numCh: DWORD; channelInfo: POINTER TO ADVChannelInfo; iTsk: DINT; iCon: WORD; iCh: DWORD; i: DINT; _tmpConnList: COL.IList; elem: COL.IUlintElement; itf: COL.IElement; tmpCh: POINTER TO ADVChannelInfo; lastE: DINT; e: COL.COLLECTION_ERROR; e1: Error; END_VAR VAR_INST lF: COL.ListFactory; END_VAR IF outputChannels.CountElements() > 0 OR inputChannels.CountElements() > 0 THEN RETURN; END_IF _tmpConnList := lF.CreateDynamicList(16, 16); //Iterate through all IO tasks FOR iTsk := 0 TO numTasks - 1 DO ioTask := ADR(IoConfig_Globals.pIoConfigTaskMap[iTsk]); //Store the type of the task (Input or Output) tType := ioTask^.wType; numCon := ioTask^.wNumOfConnectorMap; //Iterate through all connectors of the task FOR iCon := 0 TO numCon - 1 DO connector := ADR(ioTask^.pConnectorMapList[iCon]); numCh := connector^.dwNumOfChannels; //Iterate through all channels of the connector FOR iCh := 0 TO numCh - 1 DO //Create a new channel info object and fill it with the address, connector and size of the channel //Connectors is address of field connector in this case like EtherCAT slave //Address is the address of the IOMap //Size is the size of channel data in bits in IOMap channelInfo := __NEW(ADVChannelInfo); channelInfo^.addr := connector^.pChannelMapList[iCh].pbyIecAddress; channelInfo^.connectorField := connector^.pConnector; channelInfo^.size := connector^.pChannelMapList[iCh].wSize; //We put the channel info a temporary ordered list //Order is based on the address of IOMap lastE := TO_DINT(_tmpConnList.CountElements()) - 1; FOR i := 0 TO lastE DO _tmpConnList.GetElementAt(udiPosition := TO_UDINT(i), itfElement => itf); __QUERYINTERFACE(itf, elem); {warning disable C0033} tmpCh := TO___UXINT(elem.UlintValue); {warning restire C0033} //If the address of the channel is smaller than the address of the channel in the list IF tmpCh^.addr > channelInfo^.addr THEN //Insert the channel in the list at the current position _tmpConnList.InsertElementAt(TO_UDINT(i), ulintFactory.Create(TO_ULINT(channelInfo))); //Clear the channel info pointer channelInfo := 0; //Exit the loop i := lastE + 1; END_IF END_FOR //If the channel info is not 0, it means that the channel was not inserted in the list IF channelInfo <> 0 THEN //Add the channel to the end of the list elem := ulintFactory.Create(TO_ULINT(channelInfo)); _tmpConnList.AddElement(elem); END_IF END_FOR //Iterate temporary list and add the channels to the input or output list lastE := TO_DINT(_tmpConnList.CountElements()) - 1; FOR i := 0 TO lastE DO _tmpConnList.GetElementAt(udiPosition := TO_UDINT(i), itfElement => itf); __QUERYINTERFACE(itf, elem); {warning disable C0033} tmpCh := TO___UXINT(elem.UlintValue); {warning restire C0033} //If type is input, add the channel to the input list IF tType = TaskMapTypes.TMT_INPUTS THEN e := inputChannels.AddElement(ulintFactory.Create(TO_ULINT(tmpCh))); //If type is output, add the channel to the output list ELSIF tType = TaskMapTypes.TMT_OUTPUTS THEN e := outputChannels.AddElement(ulintFactory.Create(TO_ULINT(tmpCh))); ELSE __DELETE(tmpCh); END_IF END_FOR //Clear the temporary list _tmpConnList.RemoveAllElements(); END_FOR END_FOR END_METHOD
Last updated: 2024-02-13

Post by struccc on Backtick identifiers ^{CODESYS Forge talk (Post)}
Important: ` - Backtick - ASCII 96 ' - Apostrophe or Single Quote - ASCII 39 In the online help for some reason it renders ’ ... The only issue I don't get, why identifiers are still case-insensitive, even within `backtricks`? `mPa` and `MPa` for milli-, mega Pascal are the same identifiers, unfortunately... Is this a bug or a feature? Otherwise can do pretty nasty things with it: // A practical (?) ASCII table served as crazy strict enumeration // Just for hangover Monday mornings {attribute 'qualified_only'} {attribute 'strict'} TYPE ASCII : ( NULL := 16#00, START_OF_HEADING := 16#01, START_OF_TEXT := 16#02, END_OF_TEXT := 16#03, END_OF_TRANSMISSION := 16#04, ENQUIRY := 16#05, BELL := 16#06, ACKNOWLEDGE := 16#07, BACKSPACE := 16#08, HORIZONTAL_TAB := 16#09, LINE_FEED := 16#0A, VERTICAL_TAB := 16#0B, FORM_FEED := 16#0C, CARRIAGE_RETURN := 16#0D, SHIFT_OUT := 16#0E, SHIFT_IN := 16#0F, DATA_LINK_ESCAPE := 16#10, DEVICE_CONTROL_1 := 16#11, DEVICE_CONTROL_2 := 16#12, DEVICE_CONTROL_3 := 16#13, DEVICE_CONTROL_4 := 16#14, NEGATIVE_ACKNOWLEDGE := 16#15, SYNCHRONOUS_IDLE := 16#16, END_OF_TRANS_BLOCK := 16#17, CANCEL := 16#18, END_OF_MEDIUM := 16#19, SUBSTITUTE := 16#1A, ESCAPE := 16#1B, FILE_SEPARATOR := 16#1C, GROUP_SEPARATOR := 16#1D, RECORD_SEPARATOR := 16#1E, UNIT_SEPARATOR := 16#1F, ` ` := 16#20, `!` := 16#21, `$"` := 16#22, `#` := 16#23, `$$` := 16#24, `%` := 16#25, `&` := 16#26, `$'` := 16#27, `(` := 16#28, `)` := 16#29, `*` := 16#2A, `+` := 16#2B, `,` := 16#2C, `-` := 16#2D, `.` := 16#2E, `/` := 16#2F, `0` := 16#30, `1` := 16#31, `2` := 16#32, `3` := 16#33, `4` := 16#34, `5` := 16#35, `6` := 16#36, `7` := 16#37, `8` := 16#38, `9` := 16#39, `:` := 16#3A, `;` := 16#3B, `<` := 16#3C, `=` := 16#3D, `>` := 16#3E, `?` := 16#3F, `@` := 16#40, A := 16#41, B := 16#42, C := 16#43, D := 16#44, E := 16#45, F := 16#46, G := 16#47, H := 16#48, I := 16#49, J := 16#4A, K := 16#4B, L := 16#4C, M := 16#4D, N := 16#4E, O := 16#4F, P := 16#50, Q := 16#51, `R ` := 16#52, `S ` := 16#53, T := 16#54, U := 16#55, V := 16#56, W := 16#57, X := 16#58, Y := 16#59, Z := 16#5A, `[` := 16#5B, `\` := 16#5C, `]` := 16#5D, `^` := 16#5E, `_` := 16#5F, `agrave`:= 16#60, `a` := 16#61, `b` := 16#62, `c` := 16#63, `d` := 16#64, `e` := 16#65, `f` := 16#66, `g` := 16#67, `h` := 16#68, `i` := 16#69, `j` := 16#6A, `k` := 16#6B, `l` := 16#6C, `m` := 16#6D, `n` := 16#6E, `o` := 16#6F, `p` := 16#70, `q` := 16#71, `r` := 16#72, `s` := 16#73, `t` := 16#74, `u` := 16#75, `v` := 16#76, `w` := 16#77, `x` := 16#78, `y` := 16#79, `z` := 16#7A, `{`{} := 16#7B, `|` := 16#7C, `}` := 16#7D, `~` := 16#7E, DEL := 16#7F ) BYTE; END_TYPE
Last updated: 2025-11-05

Post by khaledkhalil on Question about the hairaichy of UaExpert ^{CODESYS Forge talk (Post)}
Hello, I am Examining this Example from Codesys Tutorial about OPC-UA server here https://www.youtube.com/watch?v=aJhzN3Uk-Do&list=PLWtD08CpmZcSV26aWh1axCAef5c5HxX-3&index=1&t=1167s. Now i am running to problem, when i create instances and i want them to appear directly under the object directory, However, it always appear with me under Objects >> Device set >> Device Name in CODESYS. I need to know how i can change the directory of my instances 'inst_3' and so on. So they can be under objects directly. I tried to modify the settings, but couldn't find any leads till now. Thanks in advance for helping
Last updated: 2024-09-12

Post by alexgooi on Function Blocks and arrays of function blocks ^{CODESYS Forge talk (Post)}
Hi Jack, I think you have to look at a FB in a different way. A Function block (Class) can contain its own data. In other words don't define loose data in your GVL, but define a instance of a FB (Object) in your GVL: Example: Function_Block Basic_Class VAR_INPUT Open_Command: BOOL; END_VAR VAR_OUTPUT Opened: BOOL; END_VAR if Open_Command then Opened := TRUE; ELSE Opened := FALSE; END_IF Global Variables Objects: ARRAY[1..100] OF Basic_Class; //Here you ar defining you objects END_VAR In your code you can directly acces the data and couple it to the IO: GVL.Objects[1].Open_Command := %IX0.0; %QX0.0 := GVL.Objects[1].Opened; //To call the code itself use: GVL.Objects[1](); If you want to take this a step further you are also able to add methods and properties to the FB/Class end thereby creating a OOIP program
Last updated: 2024-02-15

Post by e13740e on Сalling the context menu from the keyboard ^{CODESYS Forge talk (Post)}
Hello. I have a question for you, perhaps you have an answer to it. Regarding calling the Context menu from the keyboard in Devices, specifically calling the context menu window from the keyboard via an assigned combination. Goal: to have the ability to navigationally add internal Objects (Methods, Properties) to Function Blocks from the keyboard without using the mouse. The Codesys environment interface does not allow Windows access to this via Shift+F10. Externally (outside the Codesys environment), the hotkey call for the context menu (Shift+F10) from the keyboard works in various environments, but at the same time, in Codesys it does not (it doesn't work). I have already tried various options on my own to achieve this (but unsuccessfully): Tools\Customize\Keyboard\Objects (the set combination does not give the desired result) Tools\Customize\Keyboard\Objects... (the set combination is extremely useful as it provides access to adding objects directly to Devices but does not provide the ability to add an internal object (Method/Property) to a Function Block). Thank you in advance for your help!!! P.S. I have already started trying to implement a script-based solution to call the context menu via AutoHotkey - by relocating the mouse cursor to the area of the navigational selection with a subsequent call of the context menu on it and relocating the mouse cursor back to its initial position. And in order not to "reinvent the wheel," I am writing this request to you!!!
Last updated: 2025-10-05

Post by e13740e on Сalling the context menu from the keyboard ^{CODESYS Forge talk (Post)}
Hello. I have a question for you, perhaps you have an answer to it. Regarding calling the Context menu from the keyboard in Devices, specifically calling the context menu window from the keyboard via an assigned combination. Goal: to have the ability to navigationally add internal Objects (Methods, Properties) to Function Blocks from the keyboard without using the mouse. The Codesys environment interface does not allow Windows access to this via Shift+F10. Externally (outside the Codesys environment), the hotkey call for the context menu (Shift+F10) from the keyboard works in various environments, but at the same time, in Codesys it does not (it doesn't work). I have already tried various options on my own to achieve this (but unsuccessfully): Tools\Customize\Keyboard\Objects (the set combination does not give the desired result) Tools\Customize\Keyboard\Objects... (the set combination is extremely useful as it provides access to adding objects directly to Devices but does not provide the ability to add an internal object (Method/Property) to a Function Block). Thank you in advance for your help!!! P.S. I have already started trying to implement a script-based solution to call the context menu via AutoHotkey - by relocating the mouse cursor to the area of the navigational selection with a subsequent call of the context menu on it and relocating the mouse cursor back to its initial position. And in order not to "reinvent the wheel," I am writing this request to you!!!
Last updated: 2025-10-05

Post by jst69 on Python script: Launch Codesys, Execute Script, Exit Codesys ^{CODESYS Forge talk (Post)}
Dear all: Question about scripting: I am creating a .NET program that is supposed to Open codesys, open template project, export a bunch of pou, then exit codesys. Launch works, Open project works, Export works, But how do i tell codesys to close itself? I can tell windows to terminate codesys, but i would prefer to do it properly. from __future__ import print_function import sys import System proj = projects.primary # We're interested in POU nodes: POUGuid = Guid("6f9dac99-8de1-4efc-8465-68ac443b7d08") # We collect all POU nodes in that list. pous = [] # From the parent node on, we recursively add POU nodes: def CollectPous(node): if node.type == POUGuid: pous.append(node) else: for child in node.get_children(): CollectPous(child) # Now we collect all the leaf nodes. for node in proj.get_children(): CollectPous(node) # We print everything just to know what's going on. for i in pous: print("found: ", i.type, i.guid, i.get_name()) # And now we export the files. for candidate in pous: # We create a list of objects to export: # The object itsself objects = [candidate] # And sub-objects (POUs can have actions, properties, ...) objects.extend(candidate.get_children()) # And the parent folders. parent = candidate.parent while ((not parent.is_root) and parent.is_folder): objects.append(parent) parent = parent.parent # Create an unique file name: if len(sys.argv) == 1: filename = "parent\\%s.export" % (candidate.get_name()) else: filename = "%s\\%s.export" % (sys.argv[1],candidate.get_name()) # print some user information print("exporting ", len(objects), " objects to: ", filename) # and actually export the project. proj.export_xml(objects, filename) proj.close() print ("script finished.") System.exit(0) // Dont work .NET: public static void Export(string path,string proj) { if (checkSettings()) { var p = new System.Diagnostics.Process(); p.StartInfo.FileName = Properties.Settings.Default.CSVersion +"\\CODESYS\\Common\\CODESYS.exe"; p.StartInfo.Arguments = " --Profile=" + qoute(Properties.Settings.Default.CSProfile) + " --culture=en" + " --project=" + qoute(path + "\\" + proj) + " --runscript=" + Properties.Settings.Default.LastOpenProjectPath + "\\INPUT_DATA\\SCRIPT\\Export.py" + " --scriptargs:" + qoute(path) ; p.StartInfo.RedirectStandardOutput = true; p.StartInfo.UseShellExecute = false; p.StartInfo.CreateNoWindow = false; p.Start(); p.StandardOutput.ReadToEnd(); p.CloseMainWindow(); p.Close(); } }
Last updated: 2024-01-16

Post by winki on ModbusFB ClientRequest: never recovers after a single ReplyTimeout (requires full download) ^{CODESYS Forge talk (Post)}
Library: ModbusFB (CODESYS Modbus package) IDE / Runtime: CODESYS V3.5 SP___ / Control runtime ___ Target: ___ (e.g. gateway, Linux ARM64 / Debian) Slave: Modbus TCP inverter Summary I poll a Modbus TCP slave with a permanent connection: one ClientTCP (kept connected, xConnect:=TRUE) and one ClientRequestReadHoldingRegisters, triggered cyclically. Everything works fine after a fresh application download. But as soon as one single ReplyTimeout occurs (slave temporarily not answering), the request never recovers. It stays stuck and no further messages are sent, even though the TCP connection is still reported as alive. Only a full application download brings it back — an online change or a runtime reset is not enough / not what I want in production. State observed when stuck So the connection is alive, the request finished in ReplyTimeout, the FB is back to _state = None, but udiNumMsgSent no longer increases — as if a new rising edge on xExecute is no longer accepted / no longer produces a new message. My trigger logic (simplified) Each PLC cycle, in this order: If the request is fully at rest (NOT xExecute AND NOT xBusy AND NOT xDone AND NOT xError) and a read is pending, I set xExecute := TRUE. I call clientTcp() then clientRequest(rClient := clientTcp) once each, per cycle. On xDone or xError, I set xExecute := FALSE. I made sure to insert at least one full cycle with xExecute = FALSE (seen by the FB call) before re-triggering, so the falling edge is processed. Questions After a ReplyTimeout (xError = TRUE), what is the exact, correct sequence to re-trigger the same ClientRequest so a new message is actually sent again? Is a full cycle with xExecute = FALSE between two executions mandatory? Is there a known condition where, after ReplyTimeout, the ClientTCP keeps xConnected = TRUE but silently stops sending new requests (e.g. an internal request queue / _udiRequestId that gets out of sync)? udiNumMsgSent freezing at 23 while the FB shows _state = None is what puzzles me. Is the recommended pattern to drop the connection (ClientTCP.xConnect := FALSE for one cycle, then TRUE) on a request error, rather than keeping it alive? The docs state a request error does not close the connection, so I kept it open — but maybe that is the issue here. Could the large uiStartItem (50514) be relevant? It works right after download, so addressing seems correct, but I want to rule it out. Any guidance on the canonical recovery pattern after a request timeout would be greatly appreciated. Thanks!
Last updated: 2026-06-19

Sort by relevance or date