MTD516 Datasheet, PDF (12/27 Pages) List of Unclassifed Manufacturers – 16 Port 10M/100M Ethernet Switch

MYSON
TECHNOLOGY
MTD516
(Preliminary)
reset (EECLK pin is external pull_high), it enables MTD516 supporting back pressure function in
half_duplex mode; When output port buffer queue’s on_using value reach the initialization setting
threshold value (same with the Xon_TH value), MTD516 will send a JAM pattern in the input port when
it senses an incoming packet , thus force a collision to inform the remote node transmission back
off and will effectively avoid dropping packets. If the “back pressure control enable” bit is not set, and
there is no free buffer queue available for the incoming packets, the incoming packets will be dropped.
4.7 MII Polling
The MTD516 supports PHY management through the serial MDIO/MDC interface. After power on
reset, the MTD516 write related abilities to the advertisement register 4 of connected PHY devices and
restart the auto_negotiation prcedure via MDIO/MDC interface using the predefined PHY addresses
increasingly from “01000”b to “10111”b. The MTD516 will periodically and continuously poll and update
the link status and link partner’s ability which include speed, duplex mode, and 802.3x flow control
capable status of the connected PHY devices through MDIO/MDC serial interface.
4.8 MAC and DMA engine
The MTD516’s MAC performs all the functions in IEEE802.3 protocol, such as frame formatting, frame
stripping, CRC checking, bad packet dropping, defering to line traffic, and collision handling. The MAC
Rx_engine checks incoming packets and drops the bad packet which include CRC error, alignment
error, short packet (less than 64 bytes), and long packet(more than 1518 bytes or 1522 bytes when the
“VLAN tag 1522 bytes receive enable” bit is set during power on reset). Before transmission, The MAC
Tx_engine will constantly monitor the line traffic using derfering precedure. Only if it has been idle for a
96 bits time (a minimum interpacket gap time, IPG time), actual transmmission can be started. For the
half duplex mode, MAC engine will detect collision; if a collision is detected, the MAC Tx_engine will
transmit a JAM pattern and then delay the re_transmission for a random time period determined by the
back_off algorithm (MTD516 implements the truncated exponential back_off algorithm defined in IEEE
802.3 standard). For the full duplex mode, collision signal is ignored.
The MTD516’s DMA engine performs the packets non_blocking transportation between MAC engine
and external memory according to a high speed switching procedure. The switching procedure is com-
pleted by address learning/routing process and buffer queue management operation.
4.9 EEPROM interface
MTD516 provide an auto load configuration setting function through a 2 wire serial EEPROM interface
to acess external EEPROM device(24C02) after power on reset . MTD516 can easily be configured to
support port_trunking, port_ VLAN, static entry, 802.3X flow control threshold setting , flooding port
assignment ...etc functions.
4.10 Port Based VLAN
The MTD516 supports VLAN configuration by port based methodology. One port select the certain
ports to form its VLAN group by configuring the VLAN register. The packet (including broadcast packet)
is not forwarding to the destination port whose VLAN group is different from the source port.
4.11 Port Trunking
The port trunking function can also be implemented by VLAN registers. One trunk port isolates the
packet transmitting and receiving from the other trunk ports, which performs a logical trunk topology.
The non-trunk port should choose only one trunk port for transmitting, which can achieve the load bal-
ancing and maintain the packet sequences.
4.12 Memory Interface
Two kinds of external memory interface can be selected by user -- 2M byte memory (256K32 x 2) and 4
M bytes ( 512K32 x 2). Maximum 4M byte external memory can be used for packet buffering. “-10 “
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MTD516 Revision 1.2 19/06/2000