1999 Jun 14
13
Philips Semiconductors
Preliminary specication
ATSC 8-VSB demodulator and decoder
TDA8960
Transport stream interface
The transport stream interface provides an output of 8-bit
parallel MPEG-2 transport packets at a data rate of
5.38 Mbytes/s.
IMPLEMENTATION
The transport interface consists of a FIFO, which has two
tasks:
1. Removal of the field sync segment from the generation
of output data
2. Increase of the data rate of the de-randomizer from
2.69 to 5.38 MHz.
Basically the 208 bytes of a field segment (187 data bytes,
20 error correcting bytes and one segment sync byte) are
distributed over the remaining 312 data segments.
The FIFO has a depth of two data segments. As the output
data rate is 5.38 MHz we have to distribute 416 bytes, or
two field sync data segments over 312 data segments.
Every MPEG-2 transport packet corresponding to a data
segment gets a delay equal to one 5.38 MHz clock cycle.
Further, every third MPEG-2 transport packet gets an
extra delay of one 5.38 MHz transport packet.
EXTERNAL INTERFACE
The transport stream consists of four signals and one data
bus as shown in Table 4.
Table 4
Transport stream interface
FUNCTIONAL DESCRIPTION
The timing of the transport stream interface signals is shown in Fig.5.
NAME
FUNCTION
DATACLK
output clock
DATAVALID
valid demodulator output data or one valid MPEG transport packet
DATA[7 to 0]
output data stream (8-bit wide output bus)
SOP
indicates the start of a packet. It goes HIGH at the start of a packet and remains HIGH
during the rst byte of the packet, the so called sync byte
ERROR
a transport packet error indicator, which is HIGH for each 188 byte transport packet in
which the Reed Solomon decoder found more errors than it could correct
Fig.5 Timing diagram of the transport interface (normal mode).
handbook, full pagewidth
MGR604
MPEG-2
sync byte
DATACLK
DATAVALID
DATA7 to DATA0
SOP
ERROR
185.9 ns
188 bytes/34.9
s
188 bytes/34.9
s
77.5
s
00H
sync