CANopen protocol description
vacon • 19
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3
To data map the PDOs, first disable the related PDO COB ID in the pre-operational state. In the
mapping structure, write the sub-index 0 to zero (number of mapped objects). Then write the
mapping structures on the mapping parameter record, starting from the sub-index 1. When you
have written all the necessary structures, write the sub-index 0 to correspond to the mapped
objects.
Example on how to write a dummy object to RPDO1 4th entry (when using Bypass mode) is explained
below:
3.6
SYNC protocol
Sync protocol is used by PDOs when the transmission is synchronous. The sync object that is
defined by COB ID in the object 0x1005 triggers the transmission of the txPDOs, or activates the
previously received data of the rxPDO. At the default sync message the CAN-ID is 0x80. The sync
message is a zero-length message but optionally it can consist of an 8bit counter.
3.6.1
SYNC with counter
When a counter is used in a sync message, the PDOs that have a defined sync start value compare
the value against the sync message counter. The sync producer counter will overflow after it
reaches the value defined in its ‘synchronous counter overflow value’ at the object 0x1019. Also, the
sync consumer has the object 0x1019
even when the value itself is ignored. When the value of the
sync consumer is greater than zero, the sync counter handling and expecting of the sync messages
with counter are activated.
When the sync start value and the sync counter value match, the first sync message is regarded as
received.
The following figure shows an example of SYNC messaging, when the slave is configured with:
• 0x1019 - Synchronous counter 128
• 0x1800,2 - Transmission type = 2 (Cyclic, No. of SYNCs = 2)
• 0x1800,6 - Sync start value = 4
Table 28. RPDO mapping example
Transfer data (hex)
Interpretation
23 00 14 01
01 02 00 80
Write RPDO1 COB-ID (1400:01) to invalid (
0x8000 0201
)
2F 00 16 00
00
00 00 00
Write RPDO1 mapping number of entries (1600:00) to
0
23 00 16 04
10 00 06 00
Write RPDO1 4
th
entry (1600:04) to Dummy object (
00060010
)
2F 00 16 00
04
00 00 00
Write RPDO1 mapping number of entries (1600:00) to
4
23 00 14 01
01 02 00 00
Write RPDO1 COB-ID (1400:01) as valid (
0x201
)
Table 29: SYNC message
CAN ID
LENGTH
0x80
0x0
Table 30: SYNC message with counter
CAN ID
LENGTH
DATA0
0x80
0x1
Counter
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