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Where is located 8 byte header in L2 sinec L2-SEND (L2-Receive)

Created by: Mladjo at: 3/4/2009 7:50 AM (8 Replies)

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3/4/2009 7:50 AM	Rate (0)
Mladjo Posts: 14 Rating: (0)	I have project S5 to convert to S7 which use L2 communication. Therefore, all communications call now have to be on Profibus. Here is call to FB252 block in code: JUFB252 NAME:L2-SEND A-NR:KY0,50 QTYP:KSDB DBNR:KY0,100 QANF:KF+1 QLAE:KF+35 JU FB 252 NAME: L2-SEND A-NR: KY 0,50 QTYP: KS DB DBNR: KY 0,100 QANF: KF +1 QLAE: KHere is explanation in L2 documentation about L2-SEND : Request: A layer 2 service is invoked from the STEP request header and the net data to be sent. ....and.... The frame to be sent (request) consists of the 8-byte header (bytes 0 to 7) and the net data of up to 242 bytes (This header include information which I need to figure out where data are sent. I need this to findout L2 network configuration.) But I can't figure out where should I look for this 8-byte header so I can analyze it?
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3/4/2009 9:19 AM	Rate (0)
UMENCHO Diamond Expert Joined: 3/21/2006 Last visit: 11/1/2024 Posts: 10229 Rating: (1181)	Hello The data to be transmitted and received is always preceded by an 8 byte header containing control and status information for the layer 2 firmware. When calculating the memory required for transmitted and received data (parameters QLAE or ZLAE when calling a handling block) these 8 bytes must be taken into account. The data including the header form the general interface for calling the services, known as the "job buffer". The action is triggered by an application program via the job buffer. The job buffers are transferred to the interface module via the dual-port RAM using the standard handling blocks. The job buffer itself is used to transfer the parameters for correct execution of the service on the interface module. Job buffers must always be in the data block area or in the extended data block area and are restricted to a maximum length of 250 bytes. Each job buffer consists of a header and a data . More info about structure of Job buffers in manual (page 201) This is not necessary data when build S7 profibus communication. You need only to know DB for send and receive functions on both side. regards

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3/4/2009 9:50 AM	Rate (0)
Mladjo Posts: 14 Rating: (0)	Thank you for answer. So I have to look in every DB which are sent/receive as I understunf you.....I'll see. This is also I could not resolve: what is purpose of FB223 and FB224, since in this program there is several calls to FB252 and FB253 also? ( since FB223 and FB224 internaly call FB252/FB253)? This counfusing me. p.s. page 201 in what manual? in 95UL2EN.pdf page 201 is "List of Abbreviations/Glossary"
Mladjo Posts: 14 Rating: (0)	Last edited by: Mladjo at: 3/4/2009 10:41 AM Last edited by: Mladjo at: 3/4/2009 10:41 AM
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3/4/2009 1:18 PM	Rate (0)
UMENCHO Diamond Expert Joined: 3/21/2006 Last visit: 11/1/2024 Posts: 10229 Rating: (1181)	Hello OK. Let's try with your manual. (I found this is better). So, FB223 and FB224 enable you to transmit data using layer 2 services with minimal programming overhead. You only need to program these FBs once for an S5-95U. The FBs can be used for all layer 2 services. Look at SINEC L2 Interface of the S5-95U Programmable Controller (this is yours manual) page 151. For use in Step7 you need only number of DB. From this manual you can see - for each call of SEND or RECEIVE there has DB number (DBNR), start address (QANF), Send length (QLAE). In page 152 there have nice example. If everithing in your program is OK, in your screenshot job number is 50, destination DB is DB100, beginning of send/receive buffer is 1 and lenght of buffer 35. Simply your haeder datas is in the beginning of DB using for send and receive. regards

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3/5/2009 2:55 PM	Rate (0)
Mladjo Posts: 14 Rating: (0)	Hi UMENCHO! Thank you answer. This is call: [code]JU FB 252 NAME: L2-SEND A-NR: KY 0,50 QTYP: KS DB DBNR: KY 0,100 QANF: KF +1 QLAE: KF +35[/code] and this are data in DB100: 0: KH 0000 1: KH 0000 2: KH 0000 3: KH 100A 4: KH 00FF 5: KH 0002 6: KH 1000 7: KH 0000 8: KH 0086 (all others bytes are zeros) Unfortunality one data in DB100 I can't understund. If I correct, according to documentations first 8 bytes shold contain header and 6-th byte is destionation. (3: KH 100A) So here, is destination TLN number 10 or 0A ? (I dont know is this representation LSB:MSB or MSB:LSB).
Mladjo Posts: 14 Rating: (0)
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3/6/2009 9:51 PM	Rate (0)
jklm Platinum Member Joined: 12/22/2006 Last visit: 1/25/2022 Posts: 1742 Rating: (309)	Hello, You can use the Send in two ways: 1) to send data over so called "configured S5-S5 Links" In this case, the FDL service used is SDA, and there is no header in front of the data. The ANR is here between 1 and 32 for the send block 2) to use the so called layer two services. This allows to use other services than SDA, like SRD, ... Normally the A-NR used for layer two services is SEND/RECEIVE job numbers ANR (range: 134 to 186). In your example, the A-NR = 50 This ANR is normaly reserved for TF functions in the CP5430, or FMS in the CP5431. So you will have to use another ANR for layer 2 services. Let us assume that you want to use layer two services: The layer 2 header in the buffer is 8 bytes long You start sending from DW1 Therefore DW0 has no meaning : KH 0000not used Start of header: DW1: KH 0000 left 00 = FDL request, right 00 = Freely assignable ID which is returned unchanged with a confirmation DW2: KH 0000 left 00: type of service requested, where 00 = SDA (Send data with Ack) right 00: link status for a confirmation, allways 00 at SDA active side DW3: KH 100A left 10: service class, where 10 = highprio right 0A: Remote SAP, here SAP 10hex = 16 decimal DW4: KH 00FF left 00: Remote address right FF: Logical segment address, always FF Start of Data 5: KH 0002 6: KH 1000 7: KH 0000 8: KH 0086 Don't care about de logical segment. This was never used and has no meaning here. Normally with SDA, it is not common to have high prio. I would use 00 instead of 10 The remote address is 0 in your case. I guess that this is wrong. KH is hex, so if you want to send to remote partner 11 (decimal), use 0B (in hex). The remote SAP must match with what is defined at the receiver.
	Best regards jklm Suggestion was helpful? Feel free to rate it.
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3/10/2009 11:45 AM	Rate (0)
Mladjo Posts: 14 Rating: (0)	edr The remote address is 0 in your case. I guess that this is wrong. No, since system is working since '95.... Any idea then what would be receiving station then?
Mladjo Posts: 14 Rating: (0)
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3/10/2009 4:29 PM	Rate (0)
J_Bell Posts: 5822 Rating: (412)	Hello, I am sorry but I totally agree with EDR and UMENCHO. If you say your system runs since 95 I personally guess your program changes values in the DB right before the functions try to send the data. In such a case an investigation within the application should be required... but hardly possible, at least herewithin the forum. Best regards J_Bell
J_Bell Posts: 5822 Rating: (412)
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3/11/2009 7:45 AM	Rate (0)
Mladjo Posts: 14 Rating: (0)	My Step5 STL knowledge is 0. But even then I didn't find any DB header manipulation neither it that function or FB calling it. But, my coleague send me this explanation: "This two cpu communicate trough SAP, not with direct addressing" and instruct me to read 8 chapter in manual (same as UMENCHO). I careffuly read it, and come to same conclusion about address=0. So, is addressing betwean two stattion is possible only with SAP number in header (DW3), where remote address in header is irrelevant? (In above code that is DW3: KH 100A right 0A: Remote SAP, here SAP 10hex = 16 decimal, as EDR pointed)
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