
DS3181/DS3182/DS3183/DS3184
139
of a packet, data transfer will continue from the same port if the port is not almost empty. When the maximum burst
length has been transferred, data transfer will continue from the same port if no other port has data available, and
the port is not almost empty. The maximum burst length is programmable (8 – 256 bytes in four byte increments),
or can be disabled.
10.7 ATM Cell/HDLC Packet Processing
10.7.1 General Description
The ATM cell/packet processing demaps the ATM cells or HDLC packets from the receive data stream and maps
ATM cells or HDLC packets into the transmit data stream. ATM cell / packet processing supports any framed or
unframed bit synchronous or byte synchronous (octet aligned) data stream with a bit or byte rate of 52 MHz or less.
The receive direction extracts the payload from physical data stream, performs cell/packet processing on the
individual lines, and stores the cell/packet data from each line in the FIFO.
The transmit direction removes the cell/packet data for each line from the FIFO, performs cell/packet processing for
each individual line and inserts the payload into the physical data stream.
See
Figure 10-25 for the location of the Cell/Packet processing block in the DS318x devices.
Figure 10-25. ATM Cell/HDLC Packet Functional Diagram
DS3/E3
Transmit
LIU
IEEE P1149.1
JTAG Test
Access Port
Microprocessor
Interface
HDLC
FEAC
LLB
DL
B
DS3 / E3
Transmit
Formatter
DS3 / E3
Receive
Framer
Trail
Trace
Buffer
Tx Cell
Processor
Tx
FIFO
Sy
st
em
Int
er
fac
e
Rx Cell
Processor
Rx
FIFO
Tx Packet
Processor
SL
B
Rx Packet
Processor
DS3/E3
Receive
LIU
TAIS
TUA1
TX FRAC/
PLCP
RX FRAC/
PLCP
Clock Rate
Adapter
TX BERT
RX BERT
PL
B
AL
B
UA1
GEN
B3ZS/
HDB3
Encoder
B3ZS/
HDB3
Decoder
10.7.2 Features
10.7.2.1 General
Up to 4 data lines(ports) each with a bit or byte rate of 0-52 MHz
Supports bit or byte wide, framed or unframed data lines – Each port is programmable as bit synchronous
or octet aligned, the data stream can be framed or unframed, and the clock can be continuous or gapped.
Bit reordering – The received/transmitted order of the bits as transferred across the system interface is
programmable on a per-port basis. That is, in bit synchronous mode, the first bit received/transmitted by ATM
cell/packet processing can be transferred in bit position 7 (31, 23, 15, or 7) or bit position 0 (24, 16, 8, or 0). In
octet aligned mode, the bit received/transmitted by ATM cell/packet processing in bit position 7 can be
transferred in bit position 7 (31, 23, 15, or 7) or bit position 0 (24, 16, 8, or 0).