NORD Drivesystems BU0280 - Manual (Page 36)

Supplementary Manual DeviceNet for NORDAC SK 200E
36 Subject to technical amendments BU 0280 GB
4.2 DeviceNet process data
4.2.1 I/O messages
The assembly object in the DeviceNet module is static. However, it is possible to set various data lengths and
profiles in the assembly object via the parameters P160 to P165. The parameters are adopted by the bus
modules when the I/O message connection is set up.
With this it is possible to set data lengths of between 2 and 33 bytes. Any data size (in steps of 8 bits) can be
assigned to the individual FI. The lengths of the input and output data may be different.
The operating modes “Polled I/O” and “Change of state/Cyclic I/O” are fully supported by the module.
The operating mode “Bit Strobe” is subject to the restriction that the bus module may only return a maximum of
8 bytes. This must be noted for the setting of the parameters P160 and P161 – P165! Each MAC ID is
assigned a bit in the “Bit Strobe” telegram. This bit must be zero in order for the process data to be forwarded
to the FI. If the value is one, the last valid value is retained.
4.2.1.1 Transfer of 16 & 32 bit process data
The 16 and 32 bit process data must be sent in “Little Endian" format (see the following example).
Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7
Control word Setpoint 1 Setpoint 2 Setpoint 3
16 bit 32 bit (e.g. position setpoint) 16 bit (e.g. speed)
Low byte High byte Low Low byte Low High byte High Low byte High High byte Low byte High byte
4.2.1.2 Structure of the process data
Data for up to 5 devices is sent in the fragmented telegram. The transmission sequence corresponds to the
following illustration
Area 1 Area 2 Area 3 Area 4 Area 5
Bus module FI 1 FI 2 FI 3 FI 4
The data for the bus module and then for FI 1 to 4 are sent in sequence. If one of the devices is not
parameterised, the next area moves up. For example, if the bus module is not accessed, the first bytes are
assigned to FI 1.