ElmoMC CANopen DS 301 Implementation Guide - Manual (Page 33)

5.3.1 The Mapping Trigger – Transmission Type
The transmission of a TPDO and RPDO is triggered by an event, which is defined by the
PDO communication parameters: sub-index 2 of objects 0x1800 to 0x1803 (TPDO) and
sub-index 2 of objects 0x1400 to 1403 (RPDO). These object dictionary entries are
transmission types. The data type of the PDO parameter object is described in object
0x20.
PDO transmission types can be one of the following:
Transmission Type Description
0 Synchronous transmission performed once, at next SYNC.
N=1…240 Synchronous transmission performed once per 0 < N ≤ 240
accepted SYNC signals.
254 Asynchronous transmission in response to a manufacturer-
specific event.
255 Asynchronous transmission in response to a device profile (such
as DSP 402).
The Elmo drive treats type 254 and 255 alike.
5.3.2 The Synchronous Trigger
Synchronous triggers are always related to the previous SYNC reception.
The RPDO transmission type is 1. The received message is buffered but actually
transmitted for execution at the next SYNC message. Only one RPDO can be buffered for
synchronous trigger. If another RPDO arrives before the SYNC, it overrides the previous
RPDO without any notification. This method enables the simultaneous synchronization
of executing commands in several drives. When a SYNC arrives, the buffered message is
performed in the next available background cycle (Idle loop). Elmo fast reference objects
(0x2001-0x2004) are executed immediately after reception regardless of transmission
type.
With TPDOs, the message is transmitted according to transmission type value, which can
range from 1 to 240, where 1 indicates on each single SYNC, 2 means every second SYNC
message, and so on.
Note: Objects can receive data from SDOs and RPDOs simultaneously. Be aware
that when this occurs, the results are unpredictable. The final value of the object
may be either the SDO or the RPDO data.
CANopen DS 301 Implementation Guide Process Data Objects (PDOs)
MAN-CAN301IG (Ver. 2.1)
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