SAA7115 Datasheet, PDF (52/214 Pages) NXP Semiconductors – PAL/NTSC/SECAM Video Decoder with Adaptive PAL/NTSC Comb Filter, High Performance Scaler, I2C Sliced Data Readback and SQ PIXEL OUTPUT

Philips Semiconductors
CS-PD Hamburg
CVIP2
Datasheet
SAA7115
Date:
Version:
10/23/01
0.67
In ‘field mode’ the vertical trigger event gets higher priority than the vertical window definition.
The processing is normally started at line number YO and ends at line number YS, but
- if a vertical trigger occurs, before the line number YS is reached, the field processing is terminated and the next task is
checked
- if the actual line count at V-trigger is between the YO and the YS value, the task processing is started, also if the line
number YO is missed.
Continuous Mode (bit CMOD [80H[7]])
Applications, which do not use the vertical scaling, may take advantage from the ‘continuous processing mode’. In this
mode a task is started via the SWRST bit and the task enable bits TEA or TEB. The horizontal window definition keeps
it’s meaning, but YO and YS are ignored. The vertical blanking scheme is defined by the selected V-sync (see bits
V_EAV). Once started, the vertical retrigger pulses from the input are ignored and SWRST at ‘0’ is needed to stop the
task processing.
Start, Repeat and Skip
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 8.3.1.3.
Remarks:
• To activate a task the start condition must be fulfilled and, in case of FMOD = 0, 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.
8.3.1.3 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 8.3.3).
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.
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Filename: SAA7115_Datasheet.fm
page 52
Last edited by H. Lambers