SAA7118 Datasheet, PDF (63/169 Pages) NXP Semiconductors – Multistandard video decoder with adaptive comb filter and component video input

Philips Semiconductors
Multistandard video decoder with adaptive
comb filter and component video input
Preliminary specification
SAA7118
8.6.3 TEXT FIFO
The data of the terminal VBI-data slicer is collected in the
text FIFO before the transmission over the I-port is
requested (normally before the video window starts). It is
partitioned into two FIFO sections. A complete line is filled
into the FIFO before a data transfer is requested. So
normally, one line of text data is ready for transfer, while
the next text line is collected. Thus sliced text data is
delivered as a block of qualified data, without any
qualification gaps in the byte stream of the I-port.
The decoded VBI-data is collected in the dedicated
VBI-data FIFO. After capture of a line is completed, the
FIFO can be streamed through the image port, preceded
by a header, telling line number and standard.
The VBI-data period can be signalled via the sliced data
flag on pin IGP0 or IGP1. The decoded VBI-data is lead by
the ITU ancillary data header (DID[5:0] 5DH[5:0] at value
<3EH) or by SAV/EAV codes selectable by DID[5:0] at
value 3EH or 3FH. Pin IGP0 or IGP1 is set, if the first byte
of the ANC header is valid on the I-port bus. It is reset if an
SAV occurs. So it may frame multiple lines of text data
output, in case video processing starts with a distance of
several video lines to the region of text data. Valid sliced
data from the text FIFO is available on the I-port as long as
the IGP0 or IGP1 flag is set and the data qualifier is active
on pin IDQ.
The decoded VBI-data are presented in two different data
formats, controlled by bit RECODE.
• RECODE = 1: values 00H and FFH will be recoded to
even parity values 03H and FCH
• RECODE = 0: values 00H and FFH may occur in the
data stream as detected.
If the video data is transferred without any interrupt and the
video FIFO does not need to buffer any output pixel, the
text data is inserted after the end of a scaled video line,
normally during the blanking interval of the video.
8.6.5
DATA STREAM CODING AND REFERENCE SIGNAL
GENERATION (SUBADDRESSES 84H, 85H AND 93H)
As H and V reference signals are logic 1, active gate
signals are generated, which frame the transfer of the valid
output data. As an alternative to the gates, H and V trigger
pulses are generated on the rising edges of the gates.
Due to the dynamic FIFO behaviour of the complete scaler
path, the output signal timing has no fixed timing
relationship to the real-time input video stream. So fixed
propagation delays, in terms of clock cycles, related to the
analog input cannot be defined.
The data stream is accompanied by a data qualifier.
Additionally invalid data cycles are marked with code 00H.
If ITU 656 like codes are not wanted, they can be
suppressed in the output stream.
As a further option, it is possible to provide the scaler with
an external gating signal on pin ITRDY. Thereby making it
possible to hold the data output for a certain time and to
get valid output data in bursts of a guaranteed length.
The sketched reference signals and events can be
mapped to the I-port output pins IDQ, IGPH, IGPV, IGP0
and IGP1. For flexible use the polarities of all the outputs
can be modified. The default polarity for the qualifier and
reference signals is logic 1 (active).
Table 19 shows the relevant and supported SAV and EAV
coding.
8.6.4 VIDEO AND TEXT ARBITRATION (SUBADDRESS 86H)
Sliced text data and scaled video data are transferred over
the same bus, the I-port. The mixed transfer is controlled
by an arbitration circuit.
2001 May 30
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