MTD508 Myson Technology, MTD508 Datasheet - Page 10

• Manufacturer Part Number: MTD508
• Description: 8-port Switch
• Manufacturer: Myson Technology

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external pull_high), it enables the MTD508 supporting back pressure function in half-duplex mode. When output
port buffer queue’s on-using value reaches the initialization setting threshold value (same with the Xon_TH
value), the MTD508 will send a JAM pattern in the input port when it senses an incoming packet, thus forcing 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.
MII Polling
The MTD508 supports PHY management through the serial MDIO/MDC interface. After power on reset, the
MTD508 writes related abilities to the advertisement register 4 of connected PHY devices and restarts the auto-
negotiation procedure via MDIO/MDC interface using the predefined PHY addresses increasingly from ‘01000’b
to ‘01100’b. The MTD508 will lperiodically and continuously poll and update the link status and link partner’s
ability including speed, duplex mode, and 802.3x flow control capable status of the connected PHY devices
through MDIO/MDC serial interface.
MAC and DMA Engine
The MTD508’s MAC performs all functions in IEEE802.3 protocol, such as frame formatting, frame stripping,
CRC checking, bad packet dropping, deferring to line traffic, and collision handling. The MAC Rx_engine checks
incoming packets and drops the bad packet including CRC error, alignment error, short packet (less than 64
bytes) and long packet (more than 1518 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 deferring
procedure. Only if it has been idle for a half duplex mode, MAC engine will detect collision; if a collision is
detected, the MAC Tx-engine will transmit a JAM pattern and then dalay the re-transmission for a random time
period determined by the back-off algorithm (the MTD508 implements the truncated exponential back-off
algorithm defined in IEEE802.3 standard). For the full duplex mode, collision signal is ignored.
The MTD508’s DMA engine performs the packets non-blocking transmportation between MAC engine and
external memory according to a high speed swetching procedure. The switching procedure is completed by
address learning/routing process and buffer queue management operation.
EEPROM Interface
The MTD508 provides and auto load configuration setting function through a 2-wire serial EEPROM interface to
access external EEPROM device (24C02) after power on reset. The MTD508 can easily be configured to support
port-trunking, port-VLAN, static entry, 802.3x flow control threshold setting, flooding port assignment... etc
functions. The following table is the EEPROM contents mapping:
Reserved
Reserved
AgeHigh
AgeLow
VLAN0
VLAN1
VLAN2
VLAN3
VLAN4
Name
EOB
Myson-Century Technology
EEPROM
Address
00
01
02
03
04
05
06
07
08
09
Last EEPROM content address value
Aging Time bit [7:0]
Aging Time bit [15:8]
Port0 VLAN register
Port1 VLAN register
Port2 VLAN register
Port3 VLAN register
Port4 VLAN register
Reserved
Reserved
EEPROM Content Description
Value Under Basic
Recommended
MTD508
Operation
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8h13
8h01
8h2c
8hfe
8hfd
8hfb
8hf7
8hef
8hdf
8hbf