Datasheet

 2016 Microchip Technology Inc. DS00002246A-page 49
KSZ8895MQX/RQX/FQX/MLX
2 Aging Enable
1, Enable age function in the chip.
0, Disable aging function.
R/W
1
Pin LED[5][2] strap
option.
PD(0): Aging disable.
PU(1): Aging enable
(default).
Note: LED[5][2] has
internal pull up.
1
Fast Age
Enable
1 = Turn on fast age (800 µs). R/W 0
0
Aggressive
Back Off
Enable
1 = Enable more aggressive back-off algorithm in
half duplex mode to enhance performance. This is
not an IEEE standard.
R/W
0
Pin PMRXD0 strap
option.
PD(0): Disable
aggressive back off
(default).
PU(1): Aggressive
back off.
Note: PMRXD0 has
internal pull-down.
Register 4 (0x04): Global Control 2
7
Unicast Port-
VLAN
Mismatch
Discard
This feature is used for port VLAN (described in
Register 17, Register 33...).
1, all packets cannot cross VLAN boundary.
0, unicast packets (excluding unknown/multicast/
broadcast) can cross VLAN boundary.
R/W 1
6
Multicast
Storm
Protection
Disable
1, “Broadcast Storm Protection” does not include
multicast packets. Only DA=FFFFFFFFFFFF pack-
ets will be regulated.
0, “Broadcast Storm Protection” includes
DA = FFFFFFFFFFFF and DA [40] = 1 packets.
R/W 1
5
Back
Pressure
Mode
1, carrier sense based back pressure is selected.
0, collision based back pressure is selected.
R/W 1
4
Flow Control
and Back
Pressure Fair
Mode
1, fair mode is selected. In this mode, if a flow con-
trol port and a non-flow control port talk to the same
destination port, packets from the non-flow control
port may be dropped. This is to prevent the flow
control port from being flow controlled for an
extended period of time.
0, in this mode, if a flow control port and a non-flow
control port talk to the same destination port, the
flow control port will be flow controlled. This may
not be “fair” to the flow control port.
R/W 1
3
No
Excessive
Collision
Drop
1, the switch will not drop packets when 16 or more
collisions occur.
0, the switch will drop packets when 16 or more
collisions occur.
R/W
0
Pin PMRXD1 strap
option.
PD(0): (default) Drop
excessive collision
packets. PU(1): Do
not drop excessive
collision packets.
Note: PMRXD1 has
internal pull-down.
TABLE 4-2: GLOBAL REGISTER DESCRIPTIONS (CONTINUED)
Address Name Description Mode Default