ip178a ETC-unknow, ip178a Datasheet - Page 17

• Manufacturer Part Number: ip178a
• Description: 8-port 10/100 Ethernet Integrated Switch
• Manufacturer: ETC-unknow

Functional Description
Basic Operation
IP178A consists of eight switching ports. Full/half duplex
and speed of each port depends on the result of auto
negotiation of its corresponding transceiver. It is not
necessary to use an external memory to buffer packets.
Each port of IP178A has its own receive buffer
management, transmit buffer management, transmit
queue management, transmit MAC and receive MAC. All
ports share a hashing unit, a memory interface unit, an
empty buffer management, and an address table.
An incoming packet is stored to the internal memory if
the packet is error free. A packet is error free if its crc
field is correct and its length is between 64 and 1536
byte. At the same time, IP178A examines the address
field of the packet. By the way, switch learns the
locations of every station (source address) and records
them on the address table. IP178A then reads the packet
from the internal memory and sends it to the appropriate
ports according to the address table. Eventually, IP178A
supports the switching function by dropping or forwarding
the incoming packets.
Block Description
The basic function of each block in the block diagram is
illustrated in the following context. Hashing unit is
responsible to learn and to recognize address. Transmit
buffer management and receive buffer management are
responsible to store data to or to read data from the
internal memory through memory interface unit. Transmit
MAC and receive MAC interface to transceivers and
Preliminary, Specification
IP178A-DS-P05
Sep. 09, 2002
subject to change without notice
17
implement Ethernet protocol.
Receive MAC receives the incoming data from
transceiver and converts nibble data into double word
data. As a 32 bit data is ready, it feeds the data into
receive FIFO and requests receive buffer management
for data transfer. When receive buffer management
receives the request, it gets a empty block from empty
buffer management and writes the double word data to
the buffer, which is located in the internal SSRAM,
through memory interface unit. The incoming packet is
fed to hashing unit at the same time. Hashing unit
extracts the source address of incoming packet to set up
an address table. An incoming packet is dropped or
forwarded according to the table. The address table is
built in the SSRAM of IP178A.
All ports share an empty buffer management. After reset,
the empty buffer management provides 8 addresses of
empty blocks. When a packet comes in, it searches for a
new empty block. After a packet is forwarded, the
corresponding blocks are released. Empty buffer
management treats the block as an empty block and
provides its address to desired receive buffer
management. Eight addresses are always ready for
receive buffer management.
(Advance Version)
IP178A