Register communication via SDO
CANopen default setting: compact representation of analog process data
In a CANopen modules, analog signals are compact by default, and are not mapped into the process image in complex form. The PDOs are exploited optimally in this way - every four channels occupy one PDO. In complex representation, each channel requires a space of six bytes in the process image: 1 control byte and 2 data bytes in the Tx-PDO, along with 1 status byte and another 2 data bytes in the RxPDO.
Representation of the process data, however, does not permit access to the registers through the process data, because the control and status bytes are not transferred. Access to all registers in the analog signal modules therefore takes place under CANopen via service data objects (SDOs).
Special function modules: complex representation again
The control and status byte of special function modules such as fast counters (IE/IP1502), PWM outputs (IE/IP25x2) or angle/displacement measuring modules (IE/IP5x09) are also mapped under CANopen into the process image. Access to the registers of these modules is optionally possible via SDO or through process register communication.
Access to registers in the CANopen module
Access to the registers of the CANopen connection ("coupler") is made through object 0x4500. The register model contains parameters such as
- Activation of IP-Link auto-reset
- Reaction to IP-Link failure
- Display of diagnostic data
- Identification of the signal modules
- etc.
See the object description for bus node register communication (0x4500) for details, examples and the most important setting options.
Access to module registers
Access to the registers of the intelligent signal modules is made through object 0x4501. All those signal modules with their own processor have a register module containing parameters that are specific to the signal, such as
- Analog channel scaling
- Sensor type selection
- Filter settings
- etc.
The object description for extension box register communication (0x4501) contains more precise information and examples.
