KSZ8895FLXC View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
KSZ8895FLXC
Microchip Technology
'KSZ8895FLXC' PDF : 108 Pages View PDF
KSZ8895MQX/RQX/FQX/MLX
FIGURE 3-7:
DESTINATION ADDRESS RESOLUTION FLOW CHART - STAGE 2
The KSZ8895MQX/RQX/FQX/MLX will not forward the following packets:
• Error packets. These include framing errors, frame check sequence (FCS) errors, alignment errors, and illegal
size packet errors.
• IEEE 802.3x PAUSE frames. KSZ8895MQX/RQX/FQX/MLX intercepts these packets and performs full-duplex
flow control accordingly.
• “Local” packets. Based on destination address (DA) look-up, if the destination port from the look-up table matches
the port from which the packet originated, the packet is defined as local.
3.4.13 HALF-DUPLEX BACK PRESSURE
The KSZ8895MQX/RQX/FQX/MLX also provides a half-duplex back pressure option (note: this is not in IEEE 802.3
standards). The activation and deactivation conditions are the same as the ones given for full-duplex mode. If back pres-
sure is required, the KSZ8895MQX/RQX/FQX/MLX sends preambles to defer the other station's transmission (carrier
sense deference). To avoid jabber and excessive deference as defined in IEEE 802.3 standards, after a certain period
of time, the KSZ8895MQX/RQX/FQX/MLX discontinues carrier sense but raises it quickly after it drops packets to inhibit
other transmissions. This short silent time (no carrier sense) is to prevent other stations from sending out packets and
keeps other stations in a carrier sense-deferred state. If the port has packets to send during a back pressure situation,
the carrier sense-type back pressure is interrupted and those packets are transmitted instead. If there are no more pack-
ets to send, carrier sense-type back pressure becomes active again until switch resources are free. If a collision occurs,
the binary exponential back-off algorithm is skipped and carrier sense is generated immediately, reducing the chance
of further colliding and maintaining carrier sense to prevent reception of packets. To ensure no packet loss in 10BASE-
T or 100BASE-TX half-duplex modes, the user must enable the following:
2016 Microchip Technology Inc.
DS00002246A-page 31
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