Micro 850- Triggering sensor input continuously via AWA and ACB instructions

[chowam01]

I have established communication with a sensor via ASCII protocol using the Micro-850 PLC. I have a program which writes to the sensor using an AWA instruction and the sensor responds to that by sending ASCII characters to the RX buffer. Now, when I set the trigger type of the ACB block to 0 (message is triggered once), the ARD block can acquire the ASCII characters successfully. However, when I set the trigger type to 1, the ARD block only reads 0.0. What am I doing wrong? If I want the program to autonomously refresh sensor data every 1 second interval after the AWA writes to the sensor, what should I do? Please advise. I am attaching screenshot of the program for reference.

 

[drbitboy]

I don't know much about the ASCII device.


When you send the command via AWA, does the transducer send ASCII responses continuously, or does it only send one?


If it sends just one response per AWA, then you can use the AWA.DONE to trigger an ARL to read it, and then trigger the next AWA with the ARL.DONE.


If it sends responses continuously, then the ARL should be able to continuously read and parse the data.


I would use an ARL instead of ARD, so the instruction will find the <CR><LF> delimiter for you, and the code won't have to detect it and strip it.


Also, I notice the program in Post #1 has a [Set Coil] on rung 1 and a [Direct Coil] on rung 2, both writing to the bit tag DONE. The [Direct Coil] on rung 2 will always override the [Set Coil] on rung 1, so that is a programming error.

 

[JustinEnders]

Did you ever get this to work? How did you come up with the tx string (#*?)?