MC92053 Datasheet, PDF (4/6 Pages) Motorola, Inc – Quad FTTC Network Framer

System Functional Description
Downstream Data Flow
In the downstream direction, the MC92053 receives
ATM cells from an ATM-layer device. Each cell is direct-
ed to one of the four downstream framers as indicated
by the ATM layer. Each framer adds idle cells, as nec-
essary, to produce a continuous cell stream.
The ATM cell stream is randomized and then divided
into blocks of 58 bytes. The Reed-Solomon encoder
adds eight parity bytes to each block. The block is then
sent to the interleaver.
Frame headers are generated internally. The frame
headers include the control of the TDMA for the up-
stream direction. A data link byte may also be included.
Each header is randomized, and then the Reed-So-
lomon encoder adds four parity bytes.
One frame header is combined with twelve payload
blocks from the output of the interleaver to produce an
810-byte frame. Such frames are transmitted continu-
ously through the Tx PMD interface.
Upstream Data Flow
In the upstream direction, the MC92053 receives the
frames recovered by the PMD device. Each frame un-
dergoes error correction by a Reed-Solomon decoder.
The corrected frame is derandomized, and then the
frame header is separated from the ATM cell.
The frame header is processed in accordance with the
definition of the header bytes. The payload is sent to the
cell functions block. Any physical layer cells are discard-
ed, and the remaining cells are transferred to the ATM
layer using a UTOPIA-compliant interface shared by the
four framers.
Other Functions
A microprocessor interface is provided for configuration
control and status monitoring.
A standard IEEE 1149.1 boundary scan test port is pro-
vided.
Applications
The primary application of the MC92053 is to provide
TC-sublayer processing functions for a network device,
e.g., an optical network unit (ONU), in an FTTC net-
work. Figure 3 shows the location of the network device
within an FTTC network. Figure 4 shows a generic ONU
architecture using the MC92053.
The MC92053 uses an external memory for convolu-
tional interleaving of the downstream data. If interleav-
ing is not performed, the external memory is not
required.
Motorola
4
Network
Device
MC92053
Passive
Splitter
User Device
MC92052
(Set-Top Box /
Adaptor Card / etc.)
Access
Network
ONU
User Device
MC92052
(Set-Top Box /
Adaptor Card / etc.)
Network _MC92053
Device
Passive
Splitter
User Device
MC92052
(Set-Top Box /
Adaptor Card / etc.)
optical fiber
coax / copper pair
User Device
MC92052
(Set-Top Box /
Adaptor Card / etc.)
Figure 3. Typical FTTC Network
MC92053