KSZ8895MQ_12 Datasheet, PDF (58/116 Pages) Micrel Semiconductor – Integrated 5-Port 10/100 Managed Ethernet Switch with MII/RMII interface

Micrel, Inc.
KSZ8895MQ/RQ/FMQ
Global Registers (Continued)
Address Name
4
Flow Control and Back
Pressure fair Mode
Description
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.
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.
1, will accept packet sizes up to 1916 bytes (inclusive).
This bit setting will override setting from bit 1 of the
2
Huge Packet Support
same register.
0, the max packet size will be determined by bit 1 of
this register.
1, will accept packet sizes up to 1536 bytes (inclusive).
1
Legal Maximum Packet
Size Check Disable
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.
0
Reserved
N/A
Register 5 (0x05): Global Control 3
1, 802.1q VLAN mode is turned on. VLAN table needs
7
802.1q VLAN Enable
to set up before the operation.
0, 802.1q VLAN is disabled.
IGMP Snoop Enable on 1, IGMP snoop enabled. All the IGMP packets will be
6
Switch SW5-MII/RMII
forwarded to Switch MII/RMII port.
Interface
0, IGMP snoop disabled.
1, direct mode on Port 5. This is a special mode for the
Enable Direct Mode on Switch MII/RMII interface. Using preamble before
5
Switch SW5-MII/RMII
MRXDV to direct switch to forward packets, bypassing
Interface
internal look-up.
0, normal operation.
Mode
Default
R/W
1
0
Pin PMRXD1
strap option.
PD(0): (default )
Drop excessive
R/W
collision packets.
PU(1): Do Not
drop excessive
collision packets.
Note: PMRXD1
has internal pull
down.
R/W
0
0
Pin PMRXER
strap option.
PD(0): (default)
1518/1522 byte
R/W packets.
PU(1): 1536 byte
packets.
Note: PMRXER
has internal pull-
down.
RO
0
R/W
0
R/W
0
R/W
0
March 2012
58
M9999-032612-1.5