2/24/2008 9T6WP
BCM7405
Preliminary Hardware Data Module
Functional Description
06/29/07
Bro a d c o m C o rp o r a ti o n
Page 1-16
Data Transport Processor
Document
7405-1HDM00-R
D
ATA
T
RANSPORT
I/O C
ONNECTIONS
illustrates the primary data transport I/O connections to the chip pads.
Figure 1-4: Data Transport I/O Connections Diagram
Data Transport Input Bands
The data transport module provides six serial transport stream inputs. The data transport can support up to six active
external input bands with a maximum input rate of 100 Mbps per input. These six input bands are available as inputs to the
PID parsers, the PCR modules. There are several formatting options available for each of the transport stream inputs to
handle the many formats that are known to exist. Each input is independently programmed for these options in case different
inputs use different formats. For example, bit-wide and byte-wide serial sync inputs are supported as well as active low sync
signal input. Each input can be programmed to latch incoming data on either edge of the input clock. For serial MPEG stream
inputs, there is also the capability to perform sync detection in case the sync signal is not available. For other available
options, refer "Data Transport" in the BCM7405 Programmer's Register Reference Guide. The data transport module
provides one external parallel transport stream input. Input band 4 can be used as either serial or as parallel format.
Throughput Data Rate
The data transport module supports a maximum combined transport stream burst rate that can be greater than 216 Mbps
based on usage. As packets rejected by the PID parsers are discarded, a DRAM rate smoothing buffer called the RS buffer
is used to convert this burst rate to average rate of up to 216 Mbps after PID filter. Thus, the data transport module supports
a combined transport stream average rate after PID filtering of 216 Mbps. The RS buffer basically consists of transport
buffers for audio/video/system and the video multiplexing buffers as per MPEG buffer model.
Use of Multi-Stream CableCard limits this combined transport stream average rate to 200 Mbps. The downstream
descrambler throughput can also affects the combined transport stream average rate. The downstream descrambler itself
has a throughput of 216 Mbps. However, for streams that need Multi2 descrambling, this throughput rate is derated to 157
Mbps.
IB0
IB1
IB2
IB3
INPUT
BAND0
INPUT
BAND1
INPUT
BAND2
INPUT
BAND3
Input
pads
Input
pads
Input
pads
Input
pads
Output
pads
MCARD
IN
Input
pads
MCARD
OUT
Output
pads
RMX/RMXP
RMX
Output
pads
IB4/IBP4
INPUT
BAND4
Input
pads
INPUT
BAND5
Input
pads
IB5