Q PLC Communication

[WKla]

Hello, We have to configure a Q series PLC that needs to comunicate with: - 2 or 3 Modbus Slave devices (RS485) - 3 proprietary protocol devices (each use 1 serial port for communication) Which serial port module should I use: QJ71C24N or QJ71MB91. The QJ71MB91 support native modbus master/slave protocol but I didn't read nothing about supporting user protocol (like RS function in FX series). On the other hand the QJ71C24N supports a variety of methods for communication using user protocols, but it looks like it doesn't support Modbus. Are there any function blocks that I could use for implementing modbus protocol on QJ71C24N, or I should use one QJ71MB91 and one or more QJ71C24N modules. I have choose the Q03UDE CPU with Ethernet interface. Does the Ethernet interface, which is equipped with, support modbus TCP slave protocol? I'm a beginner in Q series PLC. Thank you.

[Inntele]

Modbus TCP protocol is supported by QJ71MT91 module only. Edited August 1, 2012 by Inntele

[kaare_t]

Agreed, however depending if you want RS232 or RS485 you can choose QJ71C24N-R2 or QJ71C24N-R4. That way you can use one card for two peripheral devices...

[KAZAH]

Modbus TCP protocol is supported by QJ71MT91 module only and the PLC of a series of QnU with a built-in Ethernet.

[WKla]

Hello, I have found the library for the modbus tcp (client/server) for built-in Ethernet (article id on beijer site: DSSE-8QDHC7(GX Works) or DSSE-8RHGF5(GX IEC)), but i didn't found the modbus library for QJ71C24N. I will use the built-in Ethernet with modbus tcp for local SCADA, and I think the speed is ok (article id: DSSE-8RJBX2). I think I will use the QJ71MB91 anyway, but I just want to see if it is possible to use modbus protocol with QJ71C24N module. Thank you.

[KAZAH]

this is for example

[Crossbow]

The QJ71C24N supports several built-in protocols, which can be selected and configured with GX Configurator-SC or the built-in tools in GX Works2. Modbus is one of them.

[Inntele]

Dear Crossbow, How long the QJ71C24N supports Modbus as pre-defined and where it's written?

[KAZAH]

You're not right.For this unit, there is no configurator modbus.

[Crossbow]

I am right. I just fired up GX Configurator-SC, selected the predefined protocol function, selected Schneider Electric, and then Modbus.

[KAZAH]

GX Configurator-SC works with GX Developer.What software uses WKLa we do not know.

[WKla]

I am using GX Works 1.77, but I can't seem to find the modbus protocol. The modbus option is available only when using GX Configurator-SC with GX Developer? Anyone knows if modbus can be selected in GX Works? Thank you. Edited October 23, 2012 by WKla

[WKla]

Anybody has some information? Should I install GX Configurator-SC or is it included in GX Works?

[KAZAH]

sh080921engj C:\Program Files\MELSOFT\GPPW2

[Crossbow]

GX Configurator-SC is not needed when using GX Works2. The replacement is built in.

[WKla]

Thanks to KAZAH and Crossbow, I have found the aplication and the settings for modbus communication for QJ71C24N. It looks very simple to use, but I will bother you with other questions.

[WKla]

Hello again, I have a problem with Modbus TCP/IP using built in Ethernet (article id on beijer site: DSSE-8QDHC7(GX Works)). It looks like I can only read M bits. I want to read L bits (that are latched). I have a lot of latch bits (L) that should be read and write from SCADA. If you have any suggestions, please post it fast, it is urgent! I also have an QJ71E71-100 unused module on my system. Thank you!

[kaare_t]

You cannot use the E71 card. They don't allow port numbers to be used below 1024, and ModbusTCP uses 502.

[WKla]

Regarding the settings for QJ71C24N-R4. I have accessed "tool/intellingent function module tool/serial communication module/predefined protocol support function" from GX Works menu. Added Modbus Protocol and then configured the registers for communication (see attached pictures) . I wrote the configuration to the PLC and performed Reset, Run-Stop-Run, but the communication card doesn't sent anything (the Rx, Tx leds not flicking). Any idea what am I doing wrong? Thank you.

[kaare_t]

How does your cable look like? It should be: 2-3 3-2 5-5 Latches on C24 side (and probably on the slave side too): 1-4-6 7-8 Alternatively a crossover cable can be used IF your slave device supports hardware handshakes.

[WKla]

I am using QJ71C24N-R4 (2x RS485/RS422). I didn't connect the cables to the slave device yet.

[kaare_t]

When using the Intelligent tool, did you remember to download the configuration??

[WKla]

Because I was in doubt with that I've checked the configurations with Module Read/Write /"Module Verification..." from intelligent tool menu. The configurations are identical. I don't know how to set on which port the predefined protocol is active, maybe I've made something wrong. Thank you.

[kaare_t]

Did you check the "Prohibit echo"? This ensures that you don't receive your own telegrams. I see that you are using channel 2, correct?

[WKla]

I didn't made the connections with the slave yet. Because I was in hurry today I observed that I have to use CPRTCL instruction to activate the channel 2 . Now I have an error but tomorrow I will see what it is happening. Thanks.