I'm using S7-1500 with in-rack CM PtP RS485/422 HF as Master.

I have only 1 slave. Modbus on RS-485 with 9600 baud, None parity, 8 bits + 1 stop bit.. I wish to have a simple reliable communication with this slave.

I have used the example program given in http://support.automation.siemens.com/WW/view/en/68202723 but I have not got useful results. This program works well for a while 2-3 hours and then comes up with various errors such as 81EA, 81E9 etc.. 

I have checked the slave end (Precia-Molen load-cell controller) and at that end it seems OK.

I wish to have a simple single-slave example using the basic instructions so that I can understand and get it to work reliably.

Thanks for looking in.

You're right... I'm feeling very stupid.. The error codes mostly ask to check the cable or the partner.. so "I" though perhaps not you have way of knowing what is working or not..

Of course no doubting your published code.. I want something that is easier or less round-about so I could manage a simple task. There aren't many settings on the slave side except for the basic comm parameters.. There is again a whole lot of parameters in Comm_data that we may or may-not use. All I'm looking for was a simple way of using Modbus_Comm_Load + Modbus_master with the goal of reading a single slave.  Now in contrast with other PLC makes (Schneider/ABB/AB) that I've used in the past, I find I'm dealing with something that is cumbersome and created for other purposes 

IMHO, I skipped the term. resistor as the single slave I'm talking is at a distance of less than 20 m. So I didn't see the need - I'll act on your suggestion all the same.  

The cable I'm using is a pair from Cat 5E FTP ethernet cable that is having each pair completely screened by aluminium foil.. so I guess we're noise immune.. I'm told that RS-485 anyway is highly noise proof.

Thanks for everything..