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Modbus FB ?

3/1/2010 4:23 PM	Rate (0)
svetoslavushatov Posts: 4 Rating: (0)	Hi, I would like to ask if somebody has experience on modbus FBs. My quiestion is if there restriction how many times could be used FBs for modbus comm. in one OB or one program? Also how affect this type of communication cycle time of OBs ? BR
svetoslavushatov Posts: 4 Rating: (0)
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3/2/2010 9:58 AM	Rate (0)
Wüstenräuber Gold Member Joined: 10/3/2008 Last visit: 4/15/2025 Posts: 996 Rating: (129)	Hi, which modbus FBdo you mean? If you mean modbus TCP: The modbus block itself doesn't have any restriction, how often the block is called. You have to attend the size of your cpu and the maximal count of connections for your cpu/cp. For each connection in NetPro (or in parameter DB in ModbusPN) you need 1 modbus block instance. The cycle time of an OB is not increased very high with this type of communication. In the modbus blocks are called the communication functions (AG_SEND/AG_RECV or TSEND/TRECV) and a little bit more things, but not "bricks". Wüstenräuber

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3/2/2010 10:35 AM	Rate (0)
svetoslavushatov Posts: 4 Rating: (0)	Thanks Wuestenraeuber, we are speeking for CP 341 and OPC Server (v1.1 or something). The data must be transfered is around 100 real vaues but to be on safe I will foresee 512 K. I not familiar with modbus at all so I'm trying to go deeper and for now it seems FB7 P_RCV_RK and FB8 P_SND_RK will be mine choise. I asked for OBs because application is using 317 2PN/DP and cycle is 30 -40 ms already and we have also OB35 on 500 ms. BR
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