3/8/2007 10:40 PM | |
Joined: 1/7/2006 Last visit: 11/17/2023 Posts: 2705 Rating:
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Hi, What do you have, a Modbus RTU Master or a Modbus RTU Slave? When it is a slave then for FC3 and FC6 you need a datablock that is mentioned in the slave parameters. There you have to give the first DB in the parameters. That DB then started on DBW0 for Register 1, DBW2 for Register 2 and so on. See also the handbook Loadable Driver CP 441-2 MODBUS Protocol RTU Format S7 is Slave You have also to program FB180 for the CP 441-2 to get the data transfert to the CPU and vice versa. See page 1-3 for the Holding Registers that are starting on 40001. Use of the Dongle Introduction In order to run the CP with loadable drivers, you require a dongle. When thedongle is plugged in, drivers can be loaded. Both interfaces of the CP 441-2 can operate with loadable drivers.
Before you can plug in the dongle, you must take the CP out of the rack. At the back of the CP, above the plugs for the backplane bus, there is a slot into which the dongle can be inserted.On page 3-3 you can see which dataformats can be used for which Modbus Function Code. On page 3-5 you will see the data for the holding registers. Access with Register-Orientated Function Codes Function Codes 03, 06, 16 The register-orientated function codes 03, 06, and 16 permit read and write access to the SIMATIC memory area data blocks. Calculation of the required data block number is carried out in two steps. 1) You can use the parameter assignment tool to specify a base DB number.This base DB is the first DB which can be accessed.2) The MODBUS Start_Register address (Register Number) transmitted inthe message is interpreted as follows: (picture) |
I hope that the answer will help, if you have still questions, don't hesitate to ask me. |
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3/23/2007 11:49 AM | |
Posts: 86 Rating:
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Thanks Late, I was able to get it working Regards, Techy |
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