Source String??

[posborne]

Hi everyone, I'm new to the forum and just got back into this field so any help would be appreciated.

I am trying to use a MicroLogix 1500 to control a ICS 4895 GPIB CONTROLLER to a Waveform Generator. Using RSLogix 500!

I'm using a AWA command to write the ASCII instructions to the GPIB controller but I can’t seem to be able to populate the data into the ST Data file area?

Any help would be appreciated.

Thank you,

 

[Lancie1]

Could you post your MicroLogix 1500 program? (ZIP it first, then attach the ZIPped copy to your next post).

I can’t seem to be able to populate the data into the ST Data file area?

You may not have a communications connection between your MicroLogix and the GPIB controller. Your ASCII instructions must use Channel 0 of the MicroLogix RS-232 port. Those are the first things to check.

Next, your AWA may not be set up correctly. AWA appends 2 end-of-line characters. The default is Carriage Return (CR) and Line Feed (LF). If your GPIB controller is expecting some other end-of-line characters, (maybe only 1 instead of 2) then you must change that in the RSLogix Channel 0 User Channel Configuration dialog. Before writing a string with AWA, you must first move the string, without the end-of-line character(s), into a ST-type string memory location. Then use that String as your AWA Source. You must use some type of handshaking so that your AWA knows when the GPIB is ready to receive another string. Otherwise you may overwrite lines that have not yet been read by the GPIB.

 

[posborne]

Thank you for your response. I uploaded the file for your review.
I’m using a 1500LRP I was under the impression that with the LRP I could use port 1 to write my ASCII commands to the GPIB controller? Is this not the case?
Again thank you for your help.

 

[Lancie1]

The AWA HELP file says that the Channel (not the Port which is Port 2) must be set to Channel 0. (Ssee quote below from the RSLogxix 500 Help file).

However, the MicroLogix 1500 User Manual says that for ASCII protocol, only for the 1764-LRP processor, the Channel can be set for 0 or 1 (see attached picture). Now make your choice. (If I were doing it, to make sure it will work, I would use Channel 0.)

AWA [ASCII Write with Append]
Rockwell Software

Use the AWA instruction to write characters from a source string to an external device. This instruction adds the two appended characters that you configure on the Channel 0 User (ASCII) Channel Configuration dialog. The default is a carriage return and line feed appended to the end of the string. When using this instruction you can also perform in-line indirection.

Entering Parameters
Channel is the number of the RS-232 port (must be 0)
Source is the string element you want to write.

Control is the area that stores the control register required to operate the instruction.

String Length (.LEN) is the number of characters you want to write from the source string (0-82). If you enter a 0, the entire string will be written. This is Word 1 in the control block.

Characters Sent (.POS) are the number of characters that the processor sent to the display area (0-82). This field is continuously updated during the execution of the instruction. This value can be greater than the string length if appended characters or inserted values from in-line indirection are used. If the string length is greater than 82 the string written to the destination will be truncated to 82 characters. This is Word 2 in the control block.