Ethernet; Process Image Access; Modbus Protocol - WAGO I/O-SYSTEM 750 Manual

88 • Fieldbus-specific Additions

ETHERNET

5.3 ETHERNET

5.3.1 Process Image Access

5.3.1.1 MODBUS Protocol

Bluetooth
isters. Registers can be read and written in block or individually. A register in-
cludes two bytes.
The allocation of the register to the input and output data of the module is de-
pendent on the order and type of modules.
Separated according to input and output data, the registers are first written in
ascending order with the data of the byte-oriented modules (analog and special
modules) and then with the data of the bit-oriented modules (digital modules).
The first input or output register allocated to a Bluetooth
status or control byte and an empty byte.
Connected to this are the registers for the unmasked mailbox.
If the mailbox is set to be superimposable, these registers contain mailbox or
process data. Furthermore, registers allocated to a Bluetooth
the remaining process data.
In access by blocks, the data is transmitted with a command (e.g., FC 3 – Read
Multiple Registers, FC 16 – Write Multiple Registers or FC 23 – Read/Write
Multiple Registers). In the function call up, the start address and the number
of registers to be transmitted are given. Access to the individual data then oc-
curs in the superordinate control.
The command FC 6 (Write Single Register) or the commands named above
are used for direct access to individual registers by setting the number of reg-
isters to be transmitted to one.
5.3.1.1.1 Example
A node contains the following modules with input and output process image:
3 x 750-402
1 x 750-452
1 x 750-644
1 x 750-550
1 x 750-452
1 x 750-550
1 x 750-452
1 x 750-504
The Bluetooth
of 6 bytes. The mailbox is unmasked.
®
module data is accessed with functions for reading and writing reg-
for every 4 bits of input data,
4 bytes of input data,
12 bytes of input and 12 bytes of output data,
4 bytes of output data,
4 bytes of input data,
4 bytes of output data,
4 bytes of input data,
4 bits of output data.
®
module uses a process image of 12 bytes with a mailbox size
®
module contains the
®
module contain
WAGO-I/O-SYSTEM 750
I/O Modules