WT8043
Appication Description
General Description
Figure 1-1 and 1-2 is a simplified functional block diagram of the WT8043. It
includes the following functional blocks: sync pulse polarity detector; horizontal
and vertical frequency discriminator, mode selector.
The Sync pulse polarity detector accepts separete H and V sync signals with any
polarities. It determines their polarities and sends the polarity information to the
mode selector for video mode selection. It alos generates -H and -V signals in spite
of their input polarities.
The H and V frequency discriminator determines the frequency range of H and V
sync signals. The mode selector determines which operating video mode it should
be, according to the frequency range and polarity of H and V sync signals. The
operating video modes include the standard IBM VGA (640x350, 640x400,
640x480), super VGA (800x600) and IBM8514/A (Inerlaced, Non-interlaced),
VESA VGA & SVGA mode, VESA new SVGA mode, XGA (1024x768), and
1280x1024 mode, also including NEC 24kHz and 3 VESA New 75Hz timing
modes.
The mode selector also generates output signals that represent the frequency range
of H. sync signal. The H sync signal is divided into 6 frequency ranges (3 ranges
for WT8043N20) according to Fig. 2, WT8043 has preset the discriminating points
between frequency ranges. However, it also offers the flexibility for providing
user-defined discriminating points for non-standard video modes.
The digital noise filter is used for rejecting noise on the incoming horizontal and
vertical synchronous signals. The input section uses two techniques to improve
noise rejec-tion. So the low level noise and the large short duration noise spikes
will be rejected. Horizontal synchronous pulse width under 0.56 ms and vertical
synchronous pulse width under 0.56 ms will be considered as noise.
Weltrend Semiconductor, Inc.
2F., No. 24, Industry E. 9th Rd.
Science-Based Industrial Park
Hsin-Chu, Taiwan, R.O.C.
Tel: 886-35-780241
Fax: 886-35-770419
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ETC [ ETC ]
