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PDF DMA2286 Data sheet ( Hoja de datos )
| Número de pieza | DMA2286 | |
| Descripción | C/D/D2-MAC Descrambler | |
| Fabricantes | Micronas | |
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MICRONAS
INTERMETALL
DMA 2275,
DMA 2286
C/D/D2-MAC
Descrambler
Edition May 20, 1992
6251-330-1E
MICRONAS
1 page  
DMA 2275, DMA 2286
2. Chip Architecture
Figure 2–1 shows the architecture of the descrambling
chip DMA 2286. The DMA 2275 architecture is identical
to the that of the DMA 2286, except that the sound pro-
cessor is missing. The chips can be subdivided into sev-
eral functional blocks.
DMA 2275 and DMA 2286:
Video Processor
– descrambling, panning and interpolation of the video
signal
PRBS Generator
– delivers cut points and cipher streams
Line 625 Processor
– acquisition of service identification data and real time
control information
Packet Processor
– acquisition of entitlement packets, acquisition of gen-
eral purpose packets, selection of cipher stream, des-
crambling of data packets
Interface Processor
– management of internal and external data transfer
Timing Generator
– delivers internal chip timing
DMA 2286 only:
Sound Processor
– spectrum descrambling of data burst, packet deinter-
leaving (one subframe only), sound packet processing
(one subframe only)
Baseband 8
Code
8
Converter
Video
8
Descrambler
Interpolation
Filter
Video Processor
8
Clamping + 8
8 Video Gate
Baseband
Video
PRBS
Generator
PRBS Generator
Packet
PRBS
Generator
VBI
Data
Interface Processor
Timing
Generator
Fast
Processor
Vdd
Vdd
GND
GND
DRAM
Interface
8
IM Bus
Interface
3
Timing
Generator
Packet Processor
Packet
Acquisition
Packet
Descrambler
Corrected
Packet
Data
Descrambl.
Packet
Data
Packet
Data
Burst
Data
Line 625
Acquisition
Line 625 Proc.
Spectr. Descr.
Deinterleaver
Sound
Processing
12 2
Sound
Proc.
Fig. 2–1: Block diagram of the DMA 2286
5
5 Page 
DMA 2275, DMA 2286
The buffer application (standard/ring) can be defined
with bit 5 in the buffer status register. Bit 7 allows to close
or reopen the buffer under software control. Bit 6 defines
the buffer increment. that means whether the buffer will
store full length (96 byte) packets or half length (48 byte)
packets.
Each of the 8 packet buffer is attached to a program-
mable packet filter which selects specific packets out of
the packet multiplex depending on packet address (PA),
continuity index (CI), packet type (PT) and packet ad-
dress extension (PAE). The packet address extension
can be used to select EMM packets by their specific cus-
tomer address (UCA, SCA, CCA) or to select ECM pack-
ets by command identification (CI or to select the data
group type (TG) of ‘0’ packets. This selection is done af-
ter error correction.
Each of the 8 packet filter is controlled by a set of regis-
ters located in the acquisition DRAM and programmable
by software. The ‘packet address base’ (PAB) registers
define the 10 bit packet address and the continuity in-
dex. The ‘packet address extension’ (PAE) registers de-
fine up to 36 bit of the address extension field. The ‘pack-
et selection control’ (PSC) registers define how packets
will be selected, error corrected and linked together.
The software should take care of conflicts like program-
ming different packet filters with the same conditions.
There must be at least one difference in the combination
of packet address, continuity index, packet type, and
packet location. Otherwise the result of the packet selec-
tion will be undefined.
If packet link is activated, the first packet meeting all pro-
grammed conditions is defined as sync packet. Selec-
tion of continuation packets is done according to the
packet link status. In case of CI link, the continuity index
of following packets will be ignored. In case of PT link,
the packet type selection is changed to PT2. a special bit
in the buffer status indicates if this procedure has been
activated by the first sync packet. The packets are then
stored into the packet buffer in the same order as they
are transmitted. The choice of packet link is independent
from the choice of buffer application.
Depending on the page select bit in the PSC register the
packet address extension is checked in every packet or
only in the sync packet. To select linked EMM packets by
customer address this bit should be ‘0’, to select linked
‘0’ packets by data group type this bit should be ‘1’.
7.2. Packet Descrambler
Main task of the packet descrambler is to detect those
sound or data packets that have to be descrambled.
Four different packet addresses can be recognized. Af-
ter detection of such a packet the concerning PRBS 3
generator is selected and produces an output sequence
of 720 bit to descramble the packet data. The PT–Byte
of each selected packet is decoded to disable the PRBS
3 generator output in case of BI packets (‘00’ or ‘3F’).
The packet descrambler can be switched to “automatic”
operation. In this mode the 4 center bits of the packet ad-
dress are ignored by the packet address comparator.
In case of C– or D–MAC, packets carrying one digital
component can be inserted in one or both subframes,
therefore the packet recognition will be repeated in the
second subframe if necessary.
Because the packet header is not scrambled, the packet
recognition has about 20 clock cycles to compare the
packet address before start of the descrambling se-
quence. Therefore there is only a 4 clock cycle delay be-
tween packet input and output.
Additionally, a packet gate is provided to remove pack-
ets form the packet output in case of denied access to
that particular service. These packets are not physically
removed – only the 720 bits after the packet header are
set to ‘1’.
Any other packet not selected by the packet recognition
passes through the packet descrambler unaffected but
with a delay of 4 clock periods.
The packet recognition is controlled by a set of registers
located in the acquisition DRAM and programmable by
software. The ‘scrambled packet address’ (SPA) regis-
ters define the 10 bit packet address and the ‘scrambled
packet status’ (SPS) registers define packet location
and status.
The software should take care of conflicts like program-
ming different SPA and SPS registers in the combination
of packet address and packet location. Otherwise, the
result of the packet recognition will be undefined.
11
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