WM8170 datasheet(26/41 Pages) WOLFSON

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WM8170

Product Preview Rev 1.0

WOLFSON MICROELECTRONICS LTD

PP Rev 1.0 March 2000

INTERNAL AREA PULSE GENERATOR

In addition to the INTBLCENB pulse generator described above, the WM8170 includes an

independent pulse generator which can be use to define any area within the video frame. The output

of the Area Pulse Generator can be used either independently of the INTBLCENB pulse (if the

BLCENB pulse generator is turned off using the STPANAL and STPIIR control bits), or to define

additional areas where the user wishes either the Analogue Control Loop or the IIR filter to operate.

This pulse generator works in a similar way to the pulse generator described above, but uses the

Vertical Drive (VD) and Horizontal Drive (HD) inputs, along with the Master Clock, to allow the user to

define any area within the active video signal.

The horizontal area enable operates as shown in Figure 21. The Management Interface registers

PIXDEL[11:0] and PIXWID[11:0] are used to define the pulse. The horizontal Area Pulse will have a

delay of PIXDEL+1 pixels from the falling edge of the HD input, and will be PIXWID pixels wide.

MCLK (Internal)

SHD

SHP

INTERNAL

HORIZONTAL AREA

PIXDEL+1 PIXELS

PIXWID PIXELS

EDGE WHICH

SAMPLES HD

Figure 21 Generating the Horizontal Area Pulse

The vertical area enable operates as shown in Figure 22. The Management Interface registers

LINDEL[11:0] and LINWID[11:0] are used to define the pulse. The Vertical Area Pulse will have a

delay of LINDEL HD pulses from the falling edge of the VD input, and will be LINWID HD pulses

wide.

INTERNAL

VERTICAL AREA

LINDEL HD

LINWID HD

EDGE WHICH

COUNTS ARE

REFERRED TO

Figure 22 Generating the Vertical Area Pulse

The logical combination of the active low, horizontal area pulse and the active low, vertical area pulse

is used to define the area of the input video required.

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