WAGO WAGO-I/O-SYSTEM 750 Series Manual

Also see for WAGO-I/O-SYSTEM 750 Series: Manual Manual Manual Manual Manual

Contents

WAGO WAGO-I/O-SYSTEM 750 Series Manual Manual pdf 57 page image

Fieldbus-specific behavior ï 57ETHERNETWAGO-I/O-SYSTEM 750I/O Modules4.3 ETHERNET4.3.1 Modbus protocol4.3.1.1 Accessing the process imageThe data in the AS-Interface master are accessed by means of the functions forreading and writing registers. The registers can be read and written in blocksor individually. One register contains two bytes.The assignment of the registers to the module I/O data is dependent on theorder and the type of the modules.The registers are written separately according to input and output data, inincreasing order, first with the data of the byte-orientated modules (analog andspecial modules) and then subsequently with the data of the bit-orientatedmodules (digital modules).The first input or output register, which is assigned to an AS-Interface mastermodule, contains the status / control byte and one empty byte.The registers for the permanently superimposed mailbox are attached to this.If the mailbox is set up to be superimposed, these registers contain themailbox or process data.The further registers associated with an AS-Interface master module containthe remaining process data.With blockwise access, the data are transmitted with one command (e.g. FC 3ñ Read Multiple Registers, FC 16 ñ Write Multiple Registers or FC 23 ñRead/Write Multiple Registers). The start address and the number of registersto be transmitted are specified in the function call. The individual data are thenaccessed in the higher-level controller.The command FC 6 (Write Single Register) can be used for direct access toindividual registers or the above commands can be used by setting the numberof registers to be transmitted to 1.4.3.1.1.1 ExampleLet a node contain the following modules with an input / output processimage:3 x 750-402 each with 4 bits of input data,1 x 750-452 4 bytes of input data,1 x 750-655 12 bytes of input data and 12 bytes of output data,1 x 750-550 4 bytes of output data,1 x 750-452 4 bytes of input data,1 x 750-550 4 bytes of output data,1 x 750-452 4 bytes of input data,1 x 750-504 4 bits of output data.