2. Serial RapidIO Interface > Transaction Flow
37
Tsi578 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
2.2
Transaction Flow
The Tsi578 receives a RapidIO packet on one of its RapidIO ports. After performing integrity checks,
such as validating a CRC, the interface logic locates the destination ID in the packet. The Tsi578 uses
this information to determine to which egress port the packet must be sent and whether it is a multicast
packet. It consults a user-configurable lookup table, which maps destination ID into egress port
numbers.
The RapidIO port transfers the packet to the Switch ISF where it is buffered and transferred to an
egress port or to the Multicast Engine. The Switch ISF is non-blocking, which means that all ports can
switch data at the same time as long as they are not switching data from multiple ports to a single port.
The Switch ISF manages head-of-line blocking, which means that when a packet cannot be moved to
an egress port (for example, because multiple ingress ports are trying to send to the same egress port),
the Switch ISF selects another packet to service from the same ingress port.
The ingress queue of Tsi578 can operate in two modes: store-and-forward and cut-through modes (see
“RapidIO Port x Control Independent Register” on page 319
). In store-and-forward mode, the ingress
port of the device waits for the arrival of the whole packet before sending it to the ISF. In cut-through
mode, the ingress port transmits the packet as soon as the ISF grants access (when the routing
information is received). However, in both modes the egress port always operates in cut-through mode:
the packet is immediately forwarded. A copy of the packet is saved at the egress port so that it can be
retransmitted should an error occur.
Packets delivered to a Multicast Engine (MCE) are replicated, based on user-configured
multicast
groups
. The MCE sends copies of the original packet to the egress ports in a parallel fashion.
2.3
Lookup Tables
Lookup tables (LUTs) are used to direct incoming packets to output ports. An ingress port performs
this routing operation by mapping the destination ID field of an incoming packet to an egress port
number on the RapidIO switch. The ingress port does this by using the destination ID as an index to a
lookup table containing user-defined egress port numbers.
Each RapidIO port has its own uniquely configurable lookup table. Configuration and maintenance of
the LUTs is compliant with the
RapidIO Interconnect Specification (Revision 1.3)
. All LUTs are
written simultaneously by these registers. Additionally, the LUT of each port can be accessed using
device-specific registers.
Ti
p
RapidIO provides a
stomp
function to abort partially transmitted packets that are later
determined to have data integrity errors or similar errors. This means if the Tsi578 finds that a
packet that is being cut-through has an error, it may send a stomp control symbol to notify the
receiver that the packet was in error and all received data of the erred packet should be
dropped.
Ti
p
Packets can cut-through from the ingress port to the Multicast Work Queue and from the
Multicast Work Queue to the Broadcast Buffers. A complete packet copy must be received by
a Broadcast Buffer before it attempts to forward the packet copy to the egress port.
Содержание Tsi578
Страница 1: ...IDT Tsi578 Serial RapidIO Switch User Manual June 6 2016 Titl ...
Страница 20: ...About this Document 20 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...
Страница 102: ...4 Internal Switching Fabric Packet Queuing 102 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...
Страница 228: ...11 Signals Pinlist and Ballmap 228 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...
Страница 504: ...B Clocking P_CLK Programming 504 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...
Страница 526: ...Index 526 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...