2. Serial RapidIO Interface > Overview
36
Tsi578 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
•
Proprietary registers for performance monitoring and tuning
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Both cut-through and store-and-forward modes for performance tuning
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Debug packet generation and capture
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Multicast functionality (described in
RapidIO Interconnect Specification (Revision 1.3) Part 11)
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Head-of-line blocking avoidance
2.1.2
Transaction Flow Overview
Packets and control symbols are received by the Serial RapidIO Electrical Interface (Serial MAC) and
forwarded to the RapidIO Interface (for more information on the Serial MAC, refer to
Electrical Interface” on page 65
). Received packets have their integrity verified by error checking.
Once the packet’s integrity has been verified, the destination ID of the packet is used to access the
routing lookup table to determine which port the packet should be forwarded to and whether the packet
is a multicast packet. The packet is then buffered by the Internal Switch Fabric (ISF) for transmission
to the port. After the packet is transferred to the egress port, the port transmits the packet. If a packet
fails the CRC check, the packet is discarded and the transmitter is instructed to retransmit the packet
through the use of control symbols.
The egress port receives packets to be transmitted from the ISF. The integrity of packets forwarded
through the ISF is retained by sending the CRC code received with the packet. For more information
on the input and ouput queues, refer to
.
The packet transmitter and the packet receiver cooperate to ensure that packets are never dropped
(lost). A transmitter must retain a packet in its buffers until the port receives a packet accepted control
symbol from the other end of the link.
2.1.3
Maintenance Requests
A maintenance packet is the only packet type that will be modified by the switch. If the hop count
value of the maintenance request is 0, the maintenance request is forwarded to the register bus for
processing. The register bus accesses the registers in the appropriate port. The response to the
maintenance request is compiled into a maintenance response packet and queued by the port for
transmission. Maintenance packets with a non-zero hop count value have their hop count decremented,
CRC recomputed, and are then forwarded to the port selected by the destination ID value in the look up
table.
2.1.4
Control Symbols
Control symbols received by the Tsi578 have their CRC validated, and their field values checked. If
either the CRC is incorrect or the control symbol field values are incorrect, a packet-not-accepted
control symbol is sent back and the control symbol is discarded. Otherwise, the control symbol is used
by the port for purposes of packet management in the transmit port or link maintenance.