Packet Formats

From the point of view of the RCUBE router, the packet format has three parts: header (two bytes), data (N bytes) , end of packet (one byte).

$\leftarrow$ 8Propagation direction6Header12. . . Data . . . 6End
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& router packet structure From the point of view of the protocol implemented by PCI-DDC, the packet format is more complicated: There are two packet formats, long and short. The long format is used for the standard messages, the short format is used for the short messages and the composed messages. The packet length is always a multiple of 4 bytes. One word is four bytes. A byte contains 9 bits: One bit is used to tag control characters

Sent or received byte order, for every word, is byte 0 first. Packet begins, therefore, with the High Routing Part char and ends with the EP character. A bullet means an undefined value.

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
38Byte 38Byte 2 8Byte 1 4Byte 0&
8BP8 $\bullet$ 8Low Routing Part8High Routing Part&
Header8Message Flags24Message Identifier &
30Page Remote Start Address21 1 &
32Header CRC &
8byte 18 $\bullet$ 8 $\bullet$ 8 $\bullet$ &
Data 8byte 5 8byte 48byte 38byte 2 &
8byte 9 8byte 88byte 78byte 6 &
8 $\bullet$ 8 $\bullet$ 8byte 118byte 10&
8ED1050 0 0 0 020 1 16Expected Packet Number&
End 32 Data CRC&
8EP8 $\bullet$ 8 $\bullet$ 8 $\bullet$ &

§-44pt 8Ø2Ø2Ø
§-18pt 822
822
822
82210Last Byte Address
8215CRC disable
816Last Packet
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Long packet format
$\begin{mydescription} \item[\id{Routing Part (RP)}] is the destination Node Num... ...ket(EP)}] is a control character: \verb*+1 0010 1011 (12Bh)+\end{mydescription}$

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
38Byte 38Byte 2 8Byte 1 4Byte 0&
8BP8 $\bullet$ 8Low Routing Part8High Routing Part&
Header8Message Flags24Message Identifier &
data 32Data 1 &
32Data 2 &
End 32CRC&
8EP8 $\bullet$ 8 $\bullet$ 8 $\bullet$ &

§-18pt &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Short packet format

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