Schneider Electric DS301 manual PDO data exchange

3 Basics IL•1F CANopen DS301

3.4.2PDO data exchange

	PDO Consumer	PDO Consumer
	R_PDO	R_PDO
COB-ID	Data
		CAN
T_PDO		R_PDO
PDO Producer		PDO Consumer

Figure 3.16 PDO data exchange

Data exchange with PDOs follows to the producer-consumer relation- ship and can be triggered in 3 ways

•Synchronized

•Event-driven, asynchronous

•On request of a consumer, asynchronous

The SYNC object controls synchronized data processing. Synchronous PDO messages are transmitted immediately like the standard PDO messages, but are only evaluated on the next SYNC. For example, sev- eral drives can be started simultaneously via synchronized data ex- change.

The device immediately evaluates PDO messages that are called on re- quest or in an event-driven way.

The transmission type can be specified separately for each PDO with subindex 02h (transmission type) of the PDO communication parameter. The objects are listed in 8 "Object directory".

Event-drivenThe "event" is a change of the PDO data. In this mode, the data is im- mediately transmitted after a change. Please note that in the case of, for example, a positioning movement, the actual position changes con- stantly so that a large number of PDOs is transmitted. There are two ways to avoid such a large number of PDOs:

•A) You can set an "Inhibit Timer" (object 1803h subindex 3). The PDO is not sent until after this inhibit time has passed.

•B) By using a bit mask, you can limit the check for changes (=event). See section "Bit mask for T_PDO4" for a description.

A further possibility of "creating" an event consists of activating an "Event Timer" (object 1803h subindex 5). You activate this counter by en- tering a value not equal to zero. When this counter is reached, this rep- resents an additional event. This means that the PDO is transmitted when a value changes or when the counter event occurs.

Synchronized In the case of this transmission mode, a PDO is transmitted in relation to a SYNC object. See 3.5 "Synchronization" for a detailed description.

0198441113586, V2.01, 11.2008

32 Fieldbus interface