SAA7104E Datasheet, PDF (15/70 Pages) NXP Semiconductors – Digital video encoder

Philips Semiconductors
Digital video encoder
Product specification
SAA7104E; SAA7105E
The input line length can be programmed. The field length
is always derived from the field length of the encoder and
the pixel clock frequency that is being used.
CBO acts as a data request signal. The circuit accepts
input data at a programmable number of clocks after CBO
goes active. This signal is programmable and it is possible
to adjust the following (see Figs 12 and 13):
• The horizontal offset
• The length of the active part of the line
• The distance from active start to first expected data
• The vertical offset separately for odd and even fields
• The number of lines per input field.
In most cases, the vertical offsets for odd and even fields
are equal. If they are not, then the even field will start later.
The SAA7104E; SAA7105E will also request the first input
lines in the even field, the total number of requested lines
will increase by the difference of the offsets.
As stated above, the circuit can be programmed to accept
the look-up and cursor data in the first 2 lines of each field.
The timing generator provides normal data request pulses
for these lines; the duration is the same as for regular lines.
The additional request pulses will be suppressed with
LUTL set to logic 0; see Table 109. The other vertical
timings do not change in this case, so the first active line
can be number 2, counted from 0.
7.17 Pattern generator for HD sync pulses
The pattern generator provides appropriate
synchronization patterns for the video data path in
auxiliary monitor or HDTV mode. It provides maximum
flexibility in terms of raster generation for all interlaced and
non-interlaced computer graphics or ATSC formats. The
sync engine is capable of providing a combination of
event-value pairs which can be used to insert certain
values in the outgoing data stream at specified times.
It can also be used to generate digital signals associated
with time events. These can be used as digital horizontal
and vertical synchronization signals on pins HSM_CSYNC
and VSM.
The picture position is adjustable through the
programmable relationship between the sync pulses and
the video contents.
The generation of embedded analog sync pulses is bound
to a number of events which can be defined for a line.
Several of these line timing definitions can exist in parallel.
For the final sync raster composition a certain sequence of
lines with different sync event properties has to be defined.
The sequence specifies a series of line types and the
number of occurrences of this specific line type. Once the
sequence has been completed, it restarts from the
beginning. All pulse shapes are filtered internally in order
to avoid ringing after analog post filters.
The sequence of the generated pulse stream must fit
precisely to the incoming data stream in terms of the total
number of pixels per line and lines per frame.
The sync engines flexibility is achieved by using a
sequence of linked lists carrying the properties for the
image, the lines as well as fractions of lines. Figure 3
illustrates the context between the various tables.
The first table serves as an array to hold the correct
sequence of lines that compose the synchronization
raster; it can contain up to 16 entries. Each entry holds a
4-bit index to the next table and a 10-bit counter value
which specifies how often this particular line is invoked.
If the necessary line count for a particular line exceeds the
10 bits, it has to use two table entries.
The 4-bit index in the line count array points to the line type
array. It holds up to 15 entries (index 0 is not used),
index 1 points to the first entry, index 2 to the second entry
of the line type array etc.
Each entry of the line type array can hold up to 8 index
pointers to another table. These indices point to portions of
a line pulse pattern: A line could be split up e.g. into a sync,
a blank, and an active portion followed by another blank
portion, occupying four entries in one table line.
Each index of this table points to a particular line of the
next table in the linked list. This table is called the line
pattern array and each of the up to seven entries stores up
to four pairs of a duration in pixel clock cycles and an index
to a value table. The table entries are used to define
portions of a line representing a certain value for a certain
number of clock cycles.
The value specified in this table is actually another 3-bit
index into a value array which can hold up to eight 8-bit
values. If bit 4 (MSB) of the index is logic 1, the value is
inserted into the G or Y signal, only; if bit 4 = 0, the
associated value is inserted into all three signals.
Two additional bits of the entries in the value array (LSBs
of the second byte) determine if the associated events
appear as a digital pulse on the HSM_CSYNC and/or VSM
outputs.
2004 Mar 04
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