Internet PLC Forum
General => Technical support => Topic started by: lberridge on March 18, 2009, 09:48:47 AM
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When attempting to monitor a fairly complex program running on an MD100-888 after connecting to XServer I get "No Response from Node1" after initial success.
On-Line Monitoring works fine, although very sluggish, when using TLServer.
Similar problem (commexception A0, no response from PLC) when running JAVA applet xhmi1.
Tried changing baud rate to 9600...same result.
Monitoring a very simple program (continuously sampling and displaying all eight ADC inputs) seems to work fine.
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Your program may have interfered with the communication routine. Please check the following:
1) You did not run the commands such as OUTCOMM, PRINT, NETCMD, READMODBUS, WRITEMODBUS, READMB2, WRITEMB2 on the same COMM port that is used for online monitoring.
2) You did not have a lot of LOAD_EEP or SAVE_EEP command. On the T100MD888 the system interrupt is shut off during the EEPROM read/write routine and if you have continous access to the EEP then it will affect the communication badly. Use these command sparingly usually during start up or shut down of the system.
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Thank you for your prompt reply.
My program does not use either comm port, but does access EEPROM, I believe at initialization only.
I will do some further checking.
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I found a few LOAD_EEP and SAVE_EEP statements in my program. Once they were all eliminated, on-line monitoring through XServer started working perfectly.
I never would have suspected this without your suggestion.
Perhaps a warning in the Programmer's Reference Manual is warranted.
Thanks again for your help.
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Thank you for your suggestion.
Did you use the differentiated form of custom function {dCusF} instead of the continuous {CusFn}? If you use the SAVE_EEP or LOAD_EEP in the {CusFn} then the EEPROM are read/written every scan of the ladder logic as long as the execution condition to this custom function is true. While it does no harm to read the EEP often (except affecting communication and slowing down the CPU greatly), writing to EEPROM continously can wear it out rather quickly due to the EEPROM's limited erase/write cycle and must be avoided. Always use the DM or A to Z, EMINT[1] to EMINT[16] to store frequently access data. EEPROM can be used to save data that can be loaded back into DM during initialization.
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Thanks Your Information
Best Regards
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