Siemens SINAMICS S120 Commissioning Manual page 18

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1.3 Terminology
● The data that is assigned to the PDOs
● The time at which the PDOs are transmitted (SYNC, change in object, etc.)
● The time at which emergency messages are transmitted
● ...
All the drive unit variables are accessed via objects. The SDO and PDO communication
services access the object directory of the drive unit.
PDO (process data object)
Used for accessing selected data rapidly and in real time. Mappings of certain PDOs are
preconfigured for certain variables or groups of variables.
The SDO is used to access all the other variables.
Profile
In the case of communication with bus systems, profiles are documents used for device
standardization purposes, whereby communication functions (in a communication profile),
device functions (in a device profile), or drive functions (in a drive profile) are described from
the point of view of the communication interface.
RPDO (receive PDO)
PDO is received by the device (contains the final position, for example).
SDO (service data object)
The SDO provides access to all variables in a CANopen device (in the case of drives: drive
and CANopen variables).
The SDO is generally used for configuration purposes. PDOs provide fast, real-time access
to selected variables.
SYNC (synchronization)
SYNC is a special message frame that synchronizes the CAN devices with each other. This
message frame has a very high priority.
TPDO (transmit PDO)
PDO transmitted by the drive (contains the actual position value, for example).
Variable
All the drive and CANopen functions can be accessed via variables.
Variables can be accessed via SDOs or PDOs.
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Commissioning Manual, (IH2), V2.6, 10/2008 Edition, 6SL3097-2AA00-0BP3
CANopen interface