ASCII Read on Micrologix 1500 Ch1

[Blaise79]

Good morning to all,
I need to modify an existing PLC MIcrologix 1500 configured with a Modem on Channel 1 (DF1 Full Duplex) and an interconnection to another PLC on CH0. Now the PLC sends SMS messages by modem. We want to use the modem to receive SMS. I'm testing the funtions ARD and ARL, but I receive every time the error code 09h.
Is it possible that a channel function correctly only to send?

Thanks to all

 

[widelto]

My guess is that the messages are to be send by another device, Is that device the other PLC ?
Or I misunderstood.

 

[Blaise79]

Thanks widelto,
no, now the ML1500 sends SMS by modem (RS232, 9600) attached on CH1 with AWT instruction. Now I want to receive SMS on the same channel with the same modem. When I try to use the ARD (Ascii receive) instruction it replies me the error code 09h (channel not supported).

Do I need to use other function?

Thanks

 

[Ken Roach]

Welcome to the PLCTalk forum community. This is an interesting challenge !

It is possible to use ASCII Write (AWT) and ASCII Write with Append (AWA) instructions on a SLC/MicroLogix serial port even when the port is configured for System mode and DF1 Full Duplex.

This is available because of legacy applications that needed to send AT commands to dial or configure a modem, and then send a DF1 Full Duplex PCCC command to read or write data from a PLC across that modem link.

But you can't use the ASCII Read instructions on a port that is still configured for System mode. You need to change it to User mode.


Giving up the ability to send and receive DF1/PCCC messages on that port doesn't sound like a problem, since you are using SMS, which will generally involve ASCII or Unicode strings.

 

[Blaise79]

Thanks,
but on ML1500 i think i can not modify the channel in user mode or I don't know how to do it.

I've the attached channels configuration.

 

[Ken Roach]

Thank you for pointing that out: on the MicroLogix, you don't have a User/System Mode selection like you do on the SLC-500.

Instead, just use that pull-down selector for the configuration of Channel 1, and select ASCII instead of DF1 Full Duplex.

 

[Blaise79]

Ok, thanks,
But, do you think that after do i need to modify on this plc the sms send management and on another plc the dial up call?

 

[Ken Roach]

I can't tell you anything about your SMS modem and serial protocol or how to program it. If you want to post your program and details about how your system works, maybe some other folks can give you advice.