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S7-200 CPU 224 XP free port communication.

Created by: Husam at: 1/5/2006 3:37 PM (5 Replies)

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1/5/2006 3:37 PM	Rate (0)
Husam Posts: 101 Rating: (11)	Hello I am using S7-200 Free port communication, CPU 224xp. Below is the initalization STL used: LD SM0.1 MOVB 16#09, SMB30 MOVB 16#B0, SMB87 MOVB '@', SMB89 MOVW +5, SMW90 MOVB 100, SMB94 ATCH INT_0, 23 ATCH INT_2, 9 ENI RCV VB100, 0 // the rest of the interrupts are configured. Then later on in the main program i am checking if the following message is received: LDS= "11R2@", VB100 S Report, 1// set a flag S PrepPacket, 1 // set a flag NOTE that i successfully received "11R2@", and replied through the port. HOWEVER, when the sender sends only the "@" - terminiating charecter, the PLC replies. Strange. WHY? WHY does it reply if the terminating charecter is send only? although i told it not to. Regards, Husam Othman.
Husam Posts: 101 Rating: (11)
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1/9/2006 3:48 PM	Rate (0)
Thumper Posts: 62 Rating: (19)	Greetings Husam, I just took a look at the code. I think I know what might be causing your problem. Do you clear VB100 after you read it? Potentially, just sending an EOM character would cause the receive routine to fire and unless you clear VB100 after you read it in your compare, the last message is still present. This could cause what your seeing. When you do the LDS=, try making the last line clear the string in VB100. Best Regards
Thumper Posts: 62 Rating: (19)
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1/14/2006 8:21 PM	Rate (0)
Husam Posts: 101 Rating: (11)	Hello Thumper, I could clear VB100. However, if i don't want to respond to a certain message, what do i do? knowing that the recieve module and/or send module is an interrupt based on an event number that gets triggerred whenver data is present in the free port. So, if i dont want to respond to a certain message, what should i do? Regards, Husam
Husam Posts: 101 Rating: (11)
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1/16/2006 6:08 PM	Rate (0)
Thumper Posts: 62 Rating: (19)	Hi Husam, The communications interrupt being serviced, does not mean that the data shows up in the program at that instant. The S7-200does the following to execute a complete scan: Read Inputs Process Logic Process Communication Requests Self Test Write Outputs That's right from Section 4 of the manual. If that's true then the logic is solved before the communications are processed. Your communications information shouldn't show up until the first step of the next scan. If you know what messages you're looking for, filter for them in the first few lines of logic. If the message isn't what you're supposed to see, clear it. Best Regards Thumper
Thumper Posts: 62 Rating: (19)
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1/17/2006 9:50 AM	Rate (0)
Husam Posts: 101 Rating: (11)	Hello Thumper, Thanks for your valuable info. What you're saying is very true, I am actually filtering the un-needed messages and i am clearing the sequence of virtual bytes where the message or the xmt buffer is located. However, i am seeing a 1-byte data of 0x00 being recieved on the other side. Is that normal? Regards Husam.
Husam Posts: 101 Rating: (11)
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1/18/2006 3:43 PM	Rate (0)
Thumper Posts: 62 Rating: (19)	Hi Husam, Sorry for delay in getting back to you. To answer your question, unless you're missing that byte in the clear, it's not normal. When you clear a location, it should remain clear. One of two things are going on, either something in the receive routine is getting fired after the clear, or you're using that byte somewhere else and accidentally overwritting it. I've done that often enough to bet that that's what you're going to find. Justa feeling. Best Regards Thumper
Thumper Posts: 62 Rating: (19)
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