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SAA7115 View Datasheet(PDF) - Philips Electronics

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Philips Semiconductors
CS-PD Hamburg
CVIP2
Datasheet
SAA7115
Date:
Version:
10/23/01
0.67
Remark: Due to bandwidth considerations XPSC[5:0] and XACL[5:0] can be chosen different to the mentioned equations
or Table 14, as the H-phase scaling is able to scale in the range from zooming up by factor 3 to downscale by a factor
of 10248191.
Equation for XPSC[5:0] calculation is: XPSC[5:0] = lower integer ofN--N---p--p-i--xi-x--_-_--o--i-nu----t
where,
the range is 1 to 63 (value 0 is not allowed);
Npix_in = number of input pixel, and
Npix_out = number of desired output pixel over the complete horizontal scaler.
The use of the prescaler results in a XACL[5:0] and XC2_1 dependent gain amplification.
The amplification can be calculated according to the equation:
DC gain = (XC2_1 + 1) × XACL[5:0] + (1 XC2_1).
It is recommended to use sequence lengths and weights, which results in a DC gain amplification of 2N, as these
amplitudes can be renormalized by the XDCG[2:0] controlled 2--1--N-- shifter of the prescaler.
Other amplifications have to be normalized by using the following BCS control circuitry according to the equation:
CONT[7:0] = SATN[7:0] = lower integer of D-----C2----X--g-D--a-C---iG-n---[-2-×--:-0--6]---4--
Where: 2XDCG[2:0] DC gain
In these cases the prescaler has to be set to an overall gain of 1, e.g. for an accumulation sequence of ‘1 + 1 + 1’
(XACL[5:0] = 2 and XC2_1 = 0), XDCG[2:0] must be set to ‘010’, this equals 14 and the BCS has to amplify the signal
to 43 (SATN[7:0] and CONT[7:0] value = lower integer of 43 × 64).
The use of XACL[5:0] is XPSC[5:0] dependent. XACL[5:0] must be < 2 × XPSC[5:0].
XACL[5:0] can be used to find a compromise between bandwidth (sharpness) and alias effects.
Figs 27 and 28 show some resulting frequency characteristics of the prescaler.
Table 14 shows the recommended prescaler programming. Other programming settings, than given in Table 14, may
result in better alias suppression, but the resulting DC gain amplification needs to be compensated by the BCS control
For example, if XACL[5:0] = 5, XC2_1 = 1, then the DC gain = 10 and the required XDCG[2:0] = 4.
The horizontal source acquisition timing and the prescaling ratio is identical for both the luminance path and chrominance
path, but the FIR filter settings can be defined differently in the two channels.
Confidential - NDA required
Filename: SAA7115_Datasheet.fm
page 56
Last edited by H. Lambers
 

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