WT8043

· Accepting separate H&V Synchronous signals with any polarities
· Support VESA VGA (640x480, 640x400, 640x350), VESA SVGA (800x600),European SVGA (800x600), VESA new SVGA (800x600), XGA (1024x768) and 1280x1024.
· Also including NEC (24K) mode, 3 VESA New 75Hz timing modes and Apple MAC II (35k) mode.
· Capable of processing horizontal frequency from 25KHz to 80KHz
· Capable of processing vertical frequency from 50Hz to 120Hz
· Standard IBM video mode control outputs (1024x768, 640x480, 640x400,640x350)
· Six non-standard horizontal frequency control outputs with predefined frequency range. (users can define their own horizontal frequency range)
· Fixed polarity horizontal and vertical synchronous signals output
· Power supply voltage: 5V, but mode select control output and frequency discrimination control output, these open collector outputs can be combined with pull high resistor, pull up to 12V.

· Auto size control for Multi-Sync Display Monitors

The WT8043 is a silicon monolithic circuit designed for synchronous signal processing of multi-sync display monitors capable of coping with many kinds of PC's and workstations. It can be applied to display monitors supporting standard IBM VGA, VESA super VGA and IBM 8514/A video modes. It can also be used in other high-end display monitors supporting non-standard video modes with user-defined horizontal/vertical frequency ranges.

WT8043 incorporates many functional circuits, horizontal/vertical frequency discrimination, display mode selection, and synchronous pulse polarity detection, into a single chip. Therefore, by using WT8043, monitor makers can shrink the PC board size, reduce the material cost with fewer components, and reduce labor cost as well.

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.