Cirrus Logic CobraNet - Manual (Page 14)

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©
Copyright 2006 Cirrus Logic, Inc. DS651PM25
CobraNet Programmer’s Reference
Control Communications
2.2.1.2. 24-bit HMI Packet Bridge Buffer Data Format
Packet byte length is specified in the two MS bytes of the first word. The LS bytes will read
0 on receipt and must be set to 0 for transmit. Transmit byte length is rounded up to the
nearest even multiple of 4. Receive byte length indicates the actual number of bytes
received.
2.2.1.3. 32-bit HMI Packet Bridge Buffer Data Format
Packet data begins with the second word. Transmission order of each word is MH, MS,
LS, ML.
Table 3. Packet Bridge Buffer Layout, 24-bit Platforms
MS Middle LS
Word 1 Packet byte length MS Packet byte length LS unused/0
Word 2 Destination MAC byte 2 Destination MAC byte 3 unused/0
Word 2 Destination MAC byte 4 Destination MAC byte 3 unused/0
Word 3 Destination MAC byte 6 Destination MAC byte 5 unused/0
Word 4 Source MAC byte 2 Source MAC byte 1 unused/0
Word 5 Source MAC byte 4 Source MAC byte 3 unused/0
Word 6 Source MAC byte 6 Source MAC byte 5 unused/0
Word 7 Protocol identifier LS Protocol identifier MS unused/0
Word 8 Payload byte 2 Payload byte 1 unused/0
... ... ... unused/0
Word n Payload byte n Payload byte n-1 unused/0
Table 4. Packet Bridge Buffer Layout, 32-bit Platforms
MS MH ML LS
Word 1 Byte length MS Byte length LS unused/0 unused/0
Word 2 Destination MAC byte 2 Destination MAC byte 1 Destination MAC byte 4 Destination MAC byte 3
Word 3 Destination MAC byte 6 Destination MAC byte 5 Source MAC byte 1 Source MAC byte 2
Word 4 Source MAC byte 4 Source MAC byte 3 Source MAC byte 6 Source MAC byte 5
Word 5 Protocol identifier LS Protocol identifier MS Payload byte 2 Payload byte 1
Word 6 Payload byte 4 Payload byte 3 Payload byte 6 Payload byte 5
... ... ... ... ...
Word n Payload byte n-2 Payload byte n-3 Payload byte n Payload byte n-1