Entry type: FAQ, Entry ID: 19505524, Entry date: 09/20/2004
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Repeating the "BSEND" job (SFB12) when the "BRCV" block (SFB13) is in the "disabled" state ("EN_R = 0")

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QUESTION:  
In S7 communication on the S7-400 with the "BSEND" (SFB12) and "BRCV" (SFB13) blocks, is the send job repeated automatically on the system side when the "BRCV" block (SFB13) is in the "disabled" state ("EN_R = 0")? 

ANSWER:  
If the send job has been started on "BSEND" block and the recipient ("BRCV") is in the "disabled" state ("EN_R = 0"), then the "BSEND" block receives a negative acknowledgment in the user program (ERROR = 1; STATUS = 6 (decimal)). The send job is thus completed. 
There is no system-side strategy for repeating the "BSEND" job, this is the responsibility of the user. This means that the send job has to be repeated in the user program until the "BRCV" block is ready to receive the data sent - "EN_R = 1" on the "BRCV" block.