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Initiator
Request
Packet Issued
Operation
Completed for
Master
Acknowledge
Symbol
Acknowledge
Symbol
Response
Packet
Forwarded
Request Packet
Forwarded
Acknowledge
Symbol
Acknowledge
Symbol
Response Packet
Issued
Fabric
Target
Target
Completes
Operation
Operation
Issued By
Master
2.1.2.2
Example Packet – Streaming Write
SRIO Functional Description
SRIO endpoints are typically not connected directly to each other but instead have intervening connection
fabric devices. Control symbols are used to manage the flow of transactions in the SRIO physical
interconnect. Control symbols are used for packet acknowledgment, flow control information, and
maintenance functions.
Figure 5
shows how a packet progresses through the system.
Figure 5. Operation Sequence
An example packet is shown as two data streams in
Figure 6
. The first is for payload sizes of 80 bytes or
less, while the second applies to payload sizes of 80 to 256 bytes. SRIO packets must have a length that
is an even integer of 32 bits. If the combination of physical, logical and transport layers has a length that is
an integer of 16 bits, a 16-bit pad of value 0000h is added to the end of the packet, after the CRC (not
shown). Bit fields that are defined as reserved are assigned to logic 0s when generated and ignored when
received. All request and response packet formats are described in the RapidIO Input/Output Logical
Specification and MIessage Passing Logical Specification.
SPRUE13A – September 2006
Serial RapidIO (SRIO)
23
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