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TRCV_C

Created by: mbn at: 3/11/2014 2:30 PM (8 Replies)

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3/11/2014 2:30 PM	Rate (0)
mbn Regular Member Joined: 9/29/2005 Last visit: 2/24/2025 Posts: 25 Rating: (0)	Is it possible to read the LEN value of the TCP packet, instead of using a fixed max-value defined in either LEN or DATA?

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3/11/2014 2:45 PM	Rate (0)
Pittiplatsch Posts: 1368 Rating: (128)	Hello, The TRCV_C has an output parameter "RCVD_LEN", which contents thelenght of the received data. If you use a symbolic variable on "DATA", "LEN" must be "0". Greetings.
Pittiplatsch Posts: 1368 Rating: (128)
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3/11/2014 3:05 PM	Rate (0)
mbn Regular Member Joined: 9/29/2005 Last visit: 2/24/2025 Posts: 25 Rating: (0)	Thanks - but I wanted to make a dynamic LEN value. The problem is, I don't know how much data I will receive each time... I could receive 2 bytes one time, and the next time 100 bytes. I would like to be able to set the LEN parameter to fx. 160 bytes, and then receive anything UP TO 160 bytes... As it is now, I will only receive IF the data is above 160 bytes (or equal to).

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3/11/2014 3:30 PM	Rate (1)
Pittiplatsch Posts: 1368 Rating: (128)	In the describtion of TRCV_C i found the following TCP (Ad-hoc mode) The ad-hoc mode is only available with the TCP protocol variant. You use the ad-hoc mode to receive data with dynamic length with the "TRCV" instruction. You set ad-hoc mode by assigning the value "0" to the LEN parameter. All data types can be used for data blocks with standard access when you use ad-hoc mode. Only ARRAY of BYTE or data types with a length of 8 bits can be used for data blocks with optimized access (e.g., CHAR, USINT, SINT, etc.). The data length actually received is output at the RCVD_LEN parameter. TCP. For more information, open the online help of the TIA Portal...Hope, this will help you. Greetings
Pittiplatsch Posts: 1368 Rating: (128)
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This contribution was helpful to 1 thankful Users S7 AUTOMAN

3/11/2014 3:58 PM	Rate (0)
mbn Regular Member Joined: 9/29/2005 Last visit: 2/24/2025 Posts: 25 Rating: (0)	Thank you for your help. Ok, I set the LEN parameter to 0, and I define the bytes in the DATA parameter. But the problem remains; if I set the data to 4 bytes, I only see the data received if it exceeds 4 bytes. If the data is below 4 bytes, I dont receive it - and the TRCV_C block goes into error (#80C4). Is there any way to tell the block just to receive whatever it gets, without concern of the number of bytes? I have attached a screenshot of how I am using the block. Attachment tr.jpg (517 Downloads)

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3/12/2014 9:07 AM	Rate (0)
Pittiplatsch Posts: 1368 Rating: (128)	Hello mbn, do you activate the AD-HOC mode? The TRCV_C has a hidden input parameter called AD-HOC. Look at the screenshot, i attached. And also this faq may be interesting http://support.automation.siemens.com/DE/view/de/79993471 Attachment D:\ADHOC.JPG (548 Downloads)
Pittiplatsch Posts: 1368 Rating: (128)
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3/12/2014 11:20 AM	Rate (0)
mbn Regular Member Joined: 9/29/2005 Last visit: 2/24/2025 Posts: 25 Rating: (0)	Hello Pittiplatsch I du not have a hidden parameter ADHOC, as you also see in my attached screendump from yesterday. Can there be other versions of TRCV_C, I use V12 SP1 update 2! The plc is a S7-1200, is your attachment from S7-1500, or is that the same? Brg. mbn

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3/12/2014 11:33 AM	Rate (0)
Pittiplatsch Posts: 1368 Rating: (128)	oh ok, the hidden parameter are with a S7-1500. Refer to the FAQ: With S7-1200 V2, you have to declare LEN with "65535 (0xFFFF)". With S7-1200 V1, LEN must be "0".
Pittiplatsch Posts: 1368 Rating: (128)
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3/12/2014 11:43 AM	Rate (0)
mbn Regular Member Joined: 9/29/2005 Last visit: 2/24/2025 Posts: 25 Rating: (0)	Ok Thankyou very much I will test that in a day or two, but that is proberly the answer to my problems Brg. mbn

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