Problem with msg in micrologix 1400

Hello, I'm working with a master/slave setup using a micrologix 1400 master Plc and three micrologix 1200 slaves over mds sd4 radios. I am having an issue performing a successful msg instruction. Msg goes to .er. I am using channel 0 on the master as df1 half duplex master and slave on the 1200s. 1200bps and default on all timeout settings. When I download the master Plc the messages seem to work fine and I'm reading data from the slaves but after awhile it's like comm 0 shuts down and isn't sending the command to the radio. I have ran out of options to try and get it working.

Welcome to the Forum !

Describe in more detail the logic you are using to trigger MSG instructions.

Are you using Polled mode or Master-initiated communications mode ? Are any of the slave controllers executing MSG instructions of their own ?

Does the MSG instruction to one specific slave controller fail, or can it be any of them ?

What is the error code shown by the MSG instruction when the .ER bit comes on ?

Have you examined the port statistics for the serial port to see if you're getting errors or retries ?

All the msgs are being performed in the master. The process is started by timer then .dn or .er starts the next msg. I have some msgs being performed on channel 2 that are configured for modbus master then when those finish I'm doing the channel 0 msg's. Channel 2 has been in service with another radio and is setup for modbus master / slave. I'm trying to add the new sd4 radios and use channel 0. Error code 37. The msg will work fine for awhile then I stop seeing data come out of channel 0.

are all messages completing before the next message is sent? if not after the 4th buffer is full, they go to a queue. I have seen messages stop working if the queue got full, but do not remember what the error was. The error you listed shows up as a HSC error so not sure what a high speed counter has to do with it. Maybe ken can help with more info on the code.

Error code 37 is a timeout, but it can also happen if the message queue gets full and a message can't even get onto the wire.

I would have to see the code offer any opinions on how it works.

Have you determined that "data stops coming out of Channel 0" with a serial analyzer, or using the Status registers, or just by watching the Channel 0 serial port LED on the controller ?

I have seen a lot of systems that work fine when there are no timeouts or errors, but whose logic continues to execute MSG instructions when the previous ones have not completed or errored. That eventually leads to the buffers filling up.

I can tell the data transfer stops by looking on the 1400 display.