KSZ8895MQX Datasheet, PDF (49/108 Pages) Microchip Technology – Integrated 5-Port 10/100 Managed Ethernet Switch with MII/RMII Interface

KSZ8895MQX/RQX/FQX/MLX
TABLE 4-2: GLOBAL REGISTER DESCRIPTIONS (CONTINUED)
Address Name
Description
2
Aging Enable
1, Enable age function in the chip.
0, Disable aging function.
1
Fast Age
Enable
1 = Turn on fast age (800 µs).
Aggressive 1 = Enable more aggressive back-off algorithm in
0
Back Off
half duplex mode to enhance performance. This is
Enable
not an IEEE standard.
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.
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.
5
Back
Pressure
Mode
1, carrier sense based back pressure is selected.
0, collision based back pressure is selected.
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
Flow Control port may be dropped. This is to prevent the flow
4
and Back
control port from being flow controlled for an
Pressure Fair extended period of time.
Mode
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.
No
1, the switch will not drop packets when 16 or more
3
Excessive
Collision
collisions occur.
0, the switch will drop packets when 16 or more
Drop
collisions occur.
Mode
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Default
1
Pin LED[5][2] strap
option.
PD(0): Aging disable.
PU(1): Aging enable
(default).
Note: LED[5][2] has
internal pull up.
0
0
Pin PMRXD0 strap
option.
PD(0): Disable
aggressive back off
(default).
PU(1): Aggressive
back off.
Note: PMRXD0 has
internal pull-down.
1
1
1
1
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.
 2016 Microchip Technology Inc.
DS00002246A-page 49