Serial RapidIO (SRIO) User's Guide

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double-word0
4
double-wordn-1
acklD rsv
prio
tt ftype
destID
sourcelD
address
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...
double-wordn-2
CRC
PHY
LOG
TRA
LOG
TRA
PHY
5
3
2
2
8
8
29
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2
64 64
(n-4)*64
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64
16
16
n*64+32
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LOG
PHY
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TRA
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LOG
TRA
16
PHY
16
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ftype
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destID
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64
double-word8
double-word1
64
5*64
...
64
double-word9
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CRC
16
LOG
(n-9)*64
16
PHY
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64
double-wordn-2double-word11
64
(n-13)*64
...
double-wordn-1
6464 16
CRC
n*64+96
n*64+80
PHY =Physicallayer
TRA = Transportlayer
LOG=Logicallayer
2.1.2.3 Control Symbols
SCorPD parameter1stype0 stype1Parameter0 cmd CRC
533553
Delimiter 1stByte 2ndByte 3rdByte
8
SRIO Functional Description
Figure 6. 1x/4x RapidIO Packet Data Stream (Streaming-Write Class)
Note: Figure 6 assumes that addresses are 32-bit and device IDs are 8-bit.
The device ID, being an 8-bit field, will address up to 256 nodes in the system. If 16-bit addresses were
used, the system could accommodate up to 64k nodes.
The data stream includes a Cyclic Redundancy Code (CRC) field to ensure the data was correctly
received. The CRC value protects the entire packet except the ackID and one bit of the reserved PHY
field. The peripheral checks the CRC automatically in hardware. If the CRC is correct, a Packet-Accepted
control symbol is sent by the receiving device. If the CRC is incorrect, a Packet-Not-Accepted control
symbol is sent so that transmission may be retried.
Control symbols are physical layer message elements used to manage link maintenance, packet
delimiting, packet acknowledgment, error reporting, and error recovery. All transmitted data packets are
delimited by start-of-packet and end-of-packet delimiters. SRIO control symbols are 24 bits long and are
protected by their own CRC (see Figure 7 ). Control symbols provide two functions: stype0 symbols
convey the status of the port transmitting the symbol, and stype1 symbols are requests to the receiving
port or transmission delimiters. They have the following format, which is detailed in Section 3 of the
RapidIO Physical Layer 1x/4x LP-Serial Specification.
Figure 7. Serial RapidIO Control Symbol Format
Control symbols are delimited by special characters at the beginning of the symbol. If the control symbol
contains a packet delimiter(start-of-packet, end-of-packet, etc.), the special character PD (K28.3) is used.
If the control symbol does not contain a packet delimiter, the special character SC (K28.0) is used. This
use of special characters provides an early warning of the contents of the control symbol. The CRC does
not protect the special characters, but an illegal or invalid character is recognized and flagged as
Packet-Not-Accepted. Since control symbols are known length, they do not need end delimiters.
24 Serial RapidIO (SRIO) SPRUE13A – September 2006
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