SLC 500 serial communication

[wheatbread]

Hi all,

I am experiencing a 'wierd' issue with serial port on a SLC 5/05. The processor is new out of the box. I had previously loaded a program and configuration through the serial port. However, when I attempt to establish communications with RSLinx via DF1 I can no longer connect to the processor.

When I click on 'auto-configure', I get a message "failed to find baud and parity!" The baud rate on the processor is 19200 and is the same for my laptop COM1 port as well.

Interestingly, I dumped the program from the processor and was able to download the same program through the serial port. However, the same issue arose again. The serial port seems to be "dead".

I can connect to the processor via ethernet port just fine. But I will need the serial port to message to an InView display.

Any help would be greatly appreciated.

[jstolaruk]

Check channel 0's configuration when you are connected. It may have slipped out of system mode/df1 protocol into one of the four other protocols (DH485, DF1 radio modem, etc.) or user mode.

[bernie_carlton]

Alternately just check the channel 0 setup in your offline program. If it isn't DF1 then you should have recieved a warning on download about the communications being lost. If it is set up to some other mode (DH-485 etc then you may have to change RSLinx to connect. If it is ASCII mode then you probably cannot connect in that manner.

[Greg Dake]

The problem was that "user" instead of "system" was selected in the drop down box for the channel config. He was trying to communicate ASCII to a message display, and then get online with the laptop serial port.

Greg

[Ron Beaufort]

along these same lines, there is a way to have the serial port “switch over” from User to System mode ... usually this requires the use of something like HyperTerminal to send the Mode “switch over” command ...



but ...



there’s a very neat trick suggested by Mr. Ken Roach in this thread which lets you trigger a spare input (or something like that) to make the channel "switch over" ... just read on for the next couple of posts to see how it works ...

I can imagine that this would come in very handy in situations where the SLC's serial port is normally configured for the User mode - but occasionally required for making a "programming" connection ...