
1997 Jan 21
19
Philips Semiconductors
Preliminary specification
MPEG-2 systems demultiplexer
SAA7205H
Fig.8 High speed data output format.
handbook, full pagewidth
MGG769
GPO7 to GPO0
HSV
1 byte
1 byte
PID matched data
non-matching PID
tCLKOH
tCLKOL
1 byte
1 byte
DCLK
DMUX
HSE
HSSYNC
8
7.6
Interfacing to Philips SAA7201 video decoder
The Generic Data Filter (GDF) is connected to the General
Purpose interface, which shares its output bus
GPO7 to GPO0 with the high speed data interface.
This output can be used to interface with the Philips
SAA7201 video decoder. The GDF does not filter at all, it
merely passes the entire transport stream to the output in
byte format. The filter generates a GPST signal, which is a
gated byte clock, defined by a fixed high time (t
CLKOH
) and
a minimum low time (t
CLKOL
) (see Fig.9). In addition to the
strobe signal, the filter generates a GPV signal which can
be used in combination with the continuous DCLK to select
valid bytes, should a continuous clock be needed.
The filter furthermore generates a packet sync byte
indicator (GPSYNC).
It should be noted that the HS filter is programmed to
section mode (see Table 4), the general purpose output is
not available.
The general purpose interface is bidirectional and can
therefore serve as an alternative transport stream input to
the demultiplexer. The mode of the general purpose
interface is set by configuring the ‘GP_direction’ bit
(input = 1, output = 0, address 0x0700, see Table 13).
The GP pins have the following meaning when configured
to operate as inputs:
GPO7 to GPO0 = PKTDAT7 to PKTDAT0
GPST = PKTBCLK
GPSYNC = PKTSYNC
GPV = PKTDATV
HSE = PKTBAD.