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24 Curtis 1356/1356P CAN Expansion Module Manual,
Rev. A
case of a 32-bit transfer follows the same strategy, with the least significant byte
placed in data byte 5 and the most significant byte placed in data byte 8.
SDO 1356 /1356P Response (SDO-MISO)
An SDO request is always acknowledged with a response message from the
1356 /1356P. The 1356 /1356P can issue two kinds of response messages: a
normal response or, in case of an error in the request SDO, an Abort SDO
Transfer message.
SDO-MISO
(sent by 1356 /1356P in response to the system master)
Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Byte 7 Byte 8
Control CAN Object Sub-index Data: either the requested Read values,
Index or the actual Write values, or an error code
The first byte of the response contains an acknowledge code, which de-
pends on the type of transfer that was initially requested.
Action
Byte 1
Value
Read Response 0x40
Write Acknowledge 0x60
Abort SDO
0x80
Data bytes 2, 3, and 4 hold the CAN Object index and sub-index of the
request SDO.
If the SDO is a read command, bytes 5 through 8 will be filled with the
requested values, with the LSB in byte 5 and the next least significant in byte 6
and so forth. All unused bytes are set to 0.
If the SDO is a write command, bytes 5 through 8 will return the actual
value written in bytes 5 – 8. In this way, if the 1356 /1356P needs to limit or
round-down the SDO write request, the master will know—because the return
value will be different than the sent value.
If the SDO-MOSI did not properly read or tried to access a parameter
improperly, an Abort SDO Transfer will be sent. Bytes 5 through 8 will be
filled with a 32-bit error code.
0x06020000 = Object does not exist
0x06010002 = Attempt to write to a read only object
0x06040041 = Object cannot be mapped.
5 — SDO COMMUNICATIONS