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7.2.8 Fragmentation example
There are 2 kinds of fragmentation messages in the DeviceNet. One is
acknowledged fragmentation for explicit message. The other is the
unacknowledged fragmentation for IO messages. If the length of the message
data is greater than 8 bytes, this message must be fragmented to be sent.
Unacknowledged Fragmentation example
This example relates to when fragmentation of an I/O message is
performed in an Unacknowledged fashion. Unacknowledged fragmentation
consists of the back-back transmission of the fragments from the transmitting
module. The receiving module(s) returns no acknowledgments (other than the
CAN-provided Ack) on a per-fragment basis. The connection simply invokes
the Link Producer's Send service as necessary to move the message without
waiting for any specific acknowledgment from the receiving module(s).
In this demo, the polling consumed size is 10 bytes. The master must
send the fragmented messages. Data=0102030405060708090A. Assume that
an I/O Connection has been established.
Note: The slave device node is 0x09, and the master node ID is 0x0A
Master (MAC ID =0x0A)
_ Group 2 Message
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_ Destination MAC ID=0x09
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_ Message ID =5
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ID=10 001001 101. Data= 00 01 02 03 04 05 06 07
_ Group 2 Message
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_ Destination MAC ID=0x09
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_ Message ID =5
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ID=10 001001 101. Data= 81 08 09 0A
CAN-8124/ CAN-8224/ CAN-8424 User Manual (Version 2.0, Aug/2007)
_ Fragment Type= First Fragment, Fragment Count=0
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----------------------- 1
_ Fragment Type= Final Fragment, Fragment Count=1
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----------------------- final portion of the I/O data
CAN-8124/CAN-8224/CAN-8424 User Manual
Slave (MAC ID =0x09)
st
portion of the I/O data
129/153
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