
DS3181/DS3182/DS3183/DS3184
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10.9 Fractional Payload Controller
10.9.1 General Description
The Fractional Payload Controller uses a fraction of the DS3/E3 payload for ATM cell or HDLC packets. The
unused DS3/E3 payload is considered fractional overhead and can be used as a proprietary data link. The
allocation given to the fractional payload is programmable controlled using internal counters or controlled
externally. The fractional overhead data can optionally be programmed to transmit all 0’s, all 1’s, a 1010 pattern, or
insert data from an external source.
The Fractional Payload Controller demaps fractional payload and overhead data from the DS3/E3 payload in the
receive direction and maps fractional payload and overhead data into the DS3/E3 payload in the transmit direction.
The receive direction extracts the fractional payload and fractional overhead data bits from the receive DS3/E3
payload, performs fractional payload/overhead data demultiplexing, sends the fractional payload to the ATM/Packet
processor, and sends the fractional overhead data to an external interface.
The transmit direction accepts the fractional overhead from an internal register or the external interface and
fractional payload data from the ATM/Packet processor, performs fractional overhead/payload data multiplexing,
and inserts the fractional overhead and payload data into the transmit DS3/E3 payload.
See
Figure 10-36 for the location of the Fractional Payload Controller in the DS318x devices.
Figure 10-36. Fractional Payload Controller Detailed Block 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
10.9.2 Features
Programmable payload allocation – The payload data and fractional overhead allocation can be
programmed via registers.
Externally controlled payload allocation – The payload data and fractional overhead allocation can be
controlled by an external source via pins.
Fractional overhead extraction and insertion – Extracts all fractional overhead from the DS3/E3 payload
and sends it to an external serial interface. Inserts all fractional overhead from a serial interface and into the
transmit DS3/E3 payload. Optionally, the transmit fractional overhead can be set to insert all 0’s, all 1’s, or a
1010 pattern.