SAA7118 Datasheet, PDF (49/169 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
Table 9 Processing trigger and start
DESCRIPTION
Internal decoder: The processing triggers at the falling edge of the V123 pulse
(see Figs 28 (50 Hz) and 29 (60 Hz)), and starts earliest with the rising edge of the
decoder HREF at line number:
4/7 (50/60 Hz, 1st field), respectively 3/6 (50/60 Hz, 2nd field) (decoder count)
2/5 (50/60 Hz, 1st field), respectively 2/5 (50/60 Hz, 2nd field) (decoder count)
External ITU 656 stream: The processing starts earliest with SAV at line number 23
(50 Hz system), respectively line 20 (60 Hz system) (according to ITU 656 count)
XDV1
92H[5]
0
0
0
XDV0
92H[4]
1
0
0
XDH
92H[2]
0
0
0
8.4.1.2 Task handling
The task handler controls the switching between the two
programming register sets. It is controlled by
subaddresses 90H and C0H. A task is enabled via the
global control bits TEA[80H[4]] and TEB[80H[5]].
The handler is then triggered by events, which can be
defined for each register set.
In the event of a programming error the task handling and
the complete scaler can be reset to the initial states by
setting the software reset bit SWRST[88H[5]] to logic 0.
Especially if the programming registers, related acquisition
window and scale are reprogrammed while a task is active,
a software reset must be performed after programming.
Contrary to the disabling/enabling of a task, which is
evaluated at the end of a running task, when SWRST is at
logic 0 it sets the internal state machines directly to their
idle states.
The start condition for the handler is defined by bits
STRC[1:0] 90H[1:0] and means: start immediately, wait for
next V-sync, next FID at logic 0 or next FID at logic 1. The
FID is evaluated, if the vertical and horizontal offsets are
reached.
When RPTSK[90H[2]] is at logic 1 the actual running task
is repeated (under the defined trigger conditions), before
handing control over to the alternate task.
To support field rate reduction, the handler is also enabled
to skip fields (bits FSKP[2:0] 90H[5:3]) before executing
the task. A TOGGLE flag is generated (used for the correct
output field processing), which changes state at the
beginning of a task, every time a task is activated.
Examples are given in Section 8.4.1.3.
Remarks:
• To activate a task the start condition must be
fulfilled and the acquisition window offsets must be
reached.
For example, in case of ‘start immediately’, and two
regions are defined for one field, the offset of the lower
region must be greater than (offset + length) the upper
region, if not, the actual counted H and V position at the
end of the upper task is beyond the programmed offsets
and the processing will ‘wait for next V’.
• Basically the trigger conditions are checked, when a
task is activated. It is important to realize, that they are
not checked while a task is inactive. So you can not
trigger to next logic 0 or logic 1 with overlapping offset
and active video ranges between the tasks (e.g. task A
STRC[2:0] = 2, YO[11:0] = 310 and task B
STRC[2:0] = 3, YO[11:0] = 310 results in output field
rate of ⁵⁰⁄₃ Hz).
• After power-on or software reset (via
SWRST[88H[5]]) task B gets priority over task A.
8.4.1.3 Output field processing
As a reference for the output field processing, two signals
are available for the back-end hardware.
These signals are the input field ID from the scaler source
and a TOOGLE flag, which shows that an active task is
used an odd (1, 3, 5...) or even (2, 4, 6...) number of times.
Using a single or both tasks and reducing the field or frame
rate with the task handling functionality, the TOGGLE
information can be used, to reconstruct an interlaced
scaled picture at a reduced frame rate. The TOGGLE flag
isn’t synchronized to the input field detection, as it is only
dependent on the interpretation of this information by the
external hardware, whether the output of the scaler is
processed correctly (see Section 8.4.3).
With OFIDC = 0, the scalers input field ID is available as
output field ID on bit D6 of SAV and EAV, respectively on
pin IGP0 (IGP1), if FID output is selected.
When OFIDC[90H[6]] = 1, the TOGGLE information is
available as output field ID on bit D6 of SAV and EAV,
respectively on pin IGP0 (IGP1), if FID output is selected.
2001 May 30
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