MTD505 Datasheet, PDF (9/19 Pages) List of Unclassifed Manufacturers – 5 Port 10M/100M Ethernet Switch

MYSON
TECHNOLOGY
MTD505
(Preliminary)
3.0 FUNCTIONAL DESCRIPTIONS
The MTD505 is an 5 ports 10/100 Mbps fast Ethernet switch controller. It is a low cost solution for eight
ports fast Ethernet SOHO switch design. No CPU interface is required; After power on reset, MTD505
provide an auto load configuration setting function through a 2 wire serial EEPROM interface to acess
external EEPROM device, and MTD505 can easily be configured to support port_trunking, port_ VLAN,
static entry, 802.3X flow control threshold setting , flooding port assignment ...etc functions. The follow-
ing descriptions are MTD505’s major functional blocks overview.
3.1 Packet store and forwarding
The MTD505 use simple store and forward algorithm as packet switching method. Input packet from
ports will be stored to external memory first, while packet is good for forward (CRC chech ok, 64Bytes <
length < 1518Bytes, not local packets, in the same VLAN group ) , if this packet’s DA hits, than forward
this packet to the destination port, otherwise this packet will be broadcasted.
3.2 Learning and Routing
The MTD505 supports 1K or 8K MAC entries for switching. Dynamic address learning is performed by
each good unicast packet is completely received. The static address learning is achieved by EEPROM
configuration. On the other hand, the routing process is performed whenever the packet’s DA is cap-
tured. If the DA can not get a hit result, the packet is going to switch broadcast or forward to the dedi-
cated port according to the flooding control selction.
3.3 Aging
Only the dynamic address entries are scheduled in the aging machine. If one station does not transmit
any packet for a period of time, the belonging MAC address will be kicked out from the address table.
The aging out time can be program through the EEPROM auto load configuration. (Default value is 300
seconds)
3.4 Buffer Queue Management
The buffer queue manager is implemented to manage the external shared memory (use SDRAM/
SGRAM) for packet buffering. The main function of the buffer queue manager is to maintain the linked
list consists of buffer IDs, which is used to show the corresponding memory address for each incoming
packet. In addition, the buffer queue manager monitors the rested free spaces status of the external
memory, If the packet storage achieve the predefined threshold value, the buffer queue manager will
raise the alarm signal which is used to enable the flow control mechanism for avoiding transmission ID
queue overflow happening. MTD505 provide 802.3x flow control in full duplex mode and back pressure
control in half duplex mode.
3.5 Full Duplex 802.3x Flow Control
In full duplex mode, MTD505 supports the standard flow control defined in IEEE802.3x standard. It
enables the stopping of remote node transmissions via a PAUSE frame information interactoin. When
the “802.3x flow control enable” bit is set during power on reset (LEDDATA[7] pin is external pull_high),
it enables MTD505 supporting 802.3x flow control function in full_duplex mode; When output port buffer
queue’s on_using value reach the initialization setting threshold value (recommended Xon_TH = 74’h
when using 2Mbytes external memory; Xon_TH = 2e’h when using 1Mbytes external memory),
MTD505 will send out a PAUSE packet with pause time equal to FFF to stop the remote node transmis-
sion; When the output port buffer queue’s on_using value reduce to the initialization threshold
value(recommended Xoff_TH = 30’h when using 2Mbytes external memory; Xoff_TH=18’h when using
1Mbytes external memory), MTD505 will also send a PAUSE packet with pause time equal to zero to
inform the remote node to retransmit packet.
9/19
MTD505 Revision 1.2 14/04/2000