ElmoMC CANopen DS 301 Implementation Guide - Manual (Page 32)

The SDO is answered by the following:
Byte Value Description
0 0x67 Initiate download, expedited, index valid, data valid, no failure.
1 0 Index to store at.
2 0x16 Index to store at.
3 1 Sub-index to store at.
4 0 Reserved.
5 0
6 0
7 0
Table 5-2: Answered SDO
5.2 Transmit PDOs
Four transmit PDOs can be used in Elmo drives. TPDOs are used to retrieve an object
(data) from the drive. Objects that have read access and are mappable can be mapped to
each one of the TPDOs. The transmitted data inside the TPDO is ordered according to the
mapping order. The data starting from the LSB data is mapped first - in the lower index
of the relevant mapping object.
5.3 PDO Mapping
PDO mapping is a convention that assigns (maps) an object from the object dictionary
(data payload) to a PDO. Once mapped, the PDO can carry the assigned data items
without explicit reference to the object dictionary, thereby saving on communication and
CPU overhead.
Only a subset of the objects in the object dictionary can be mapped to a PDO, which can
either receive (RPDO) or transmit (TPDO). The mapping of an RPDO enables reception of
commands and variables — for example, efficient transmission of high-speed online
motion commands to the drive — whereas the mapping of a TPDO enables the drive to
send a predefined message in response to an event.
A TPDO is considered synchronous if triggered by a SYNC signal, and asynchronous if
triggered by another event.
An RPDO is buffered upon reception; it is sent for interpretation immediately (when
defined as asynchronous) or upon receipt of the next SYNC signal (when defined as
synchronous).
CANopen DS 301 Implementation Guide Process Data Objects (PDOs)
MAN-CAN301IG (Ver. 2.1)
5-3