Specifications
Micrel, Inc.
KSZ8895MQ/RQ/FMQ
Global Registers (Continued)
Address Name Description Mode Default
4
Flow Control and Back
Pressure fair Mode
1, fair mode is selected. In this mode, if a flow control
port and a non-flow control port talk to the same
destination port, then 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.
2 Huge Packet Support
1, will accept packet sizes up to 1916 bytes (inclusive).
This bit setting will override setting from bit 1 of the
same register.
0, the max packet size will be determined by bit 1 of
this register.
R/W 0
1
Legal Maximum Packet
Size Check Disable
1, will accept packet sizes up to 1536 bytes (inclusive).
0, 1522 bytes for tagged packets (not including packets
with STPID from CPU to ports 1-4), 1518 bytes for
untagged packets. Any packets larger than the
specified value will be dropped.
R/W
0
Pin PMRXER
strap option.
PD(0): (default)
1518/1522 byte
packets.
PU(1): 1536 byte
packets.
Note: PMRXER
has internal pull-
down.
0 Reserved N/A RO 0
Register 5 (0x05): Global Control 3
7 802.1q VLAN Enable
1, 802.1q VLAN mode is turned on. VLAN table needs
to set up before the operation.
0, 802.1q VLAN is disabled.
R/W 0
6
IGMP Snoop Enable on
Switch SW5-MII/RMII
Interface
1, IGMP snoop enabled. All the IGMP packets will be
forwarded to Switch MII/RMII port.
0, IGMP snoop disabled.
R/W 0
5
Enable Direct Mode on
Switch SW5-MII/RMII
Interface
1, direct mode on Port 5. This is a special mode for the
Switch MII/RMII interface. Using preamble before
MRXDV to direct switch to forward packets, bypassing
internal look-up.
0, normal operation.
R/W 0
March 12, 2014
59
Revision 1.7