Daewoo DTL- 25G6F, Service Manual

Page: 10 / 58

8
DW5457 - AE1
The DW5457-AE1 is a single chip teletext decoder for decoding World System Teletext data as well as Video
Programming System(VPS), Program Delivery Control(PDC), and Wide Screen Signalling(WSS) data used for
PALplus transmissions(line 23).
Furthermore, the device provides an integrated C500 based general-purpose, fully 8051-compatible microcontroller
with television specific hardware features. The on-chip display unit for displaying ¡ 'Level 1.5' teletext data can also be
used for customer defined on-screen displays. Up to 10 display pages are available internally.
The DW 5457-AE1 contains a slicer for VPS, WSS, PDC, and TTX, an accelerating acquisition hardware modul, a
display generator for " Level 1.5 " TTX data, and an 8bit microcontroller running at 250 ns cycle time(min.). The
controller with dedicated hardware guarantees flexibility, does most of the internal processing of TTX acquisition,
transfers data to/from the external memory interface and receives/transmits data via I
2
C-firmware user-interface. The
slicer combined with dedicated hardware stores TTX data in a VBI buffer of 764Byte. The microcontroller firmware
performs all the acquisition tasks(hamming-and parity-checks, page search and evaluation of header control bits) once
per field. Additionally, the firmware can provide high-end Teletext-features like Packet-26-handling, FLOF, TOP(in 8/10-
sheet for details).
(2) Feature
Acquisition
- Feature selection via special function register
- Simultaneous reception of TTX, VPS, PDC, and WSS(line 23)
- Fixed framing code for VPS and TTX.
- Acquisition during VBI
- Direct access to VBI RAM buffer.
- Acquisition of packets x/0 to x/24, x/27, 8/30(firmware)
- Assistance of all relevant checks(firmware)
- 1-bit framing code error tolerance(switchable)
- Complete TTX-acquisition firmware with simple user interface
Display
- Features selectable via special function register.
- 50/60/100/120-Hz display.
- Level 1.5 serial attribute display pages.
- Blanking and contrast reduction output.
- 8 direct addressable display pages.
- 12 x 10-character matrix.
- 96 character ROM(standard G0 character set).
- 156 national option characters for 12 languages(European version).
- 288 characters for X/26 display.
- 64 block mosaic graphic characters.
- 32 characters for OSD in expanded character ROM +32 characters inside OSD box.
- Saturation of basic colors adjustable in 4 steps.
- 8 fore8 background colours out of 64 colours.
- Conceal/reveal.
- Transparent foreground/background-inside/outside of a box.
- Contrast reduction inside/outside of a box.
- Cursor(colour changes from foreground to background colour).
- Flash(flash rate 1 s, independent of frame rate).
- Programmable horizontal and vertical sync delay.
- Full screen background colour in outer screen.
- Double size/double width/double height characters.
- Character shadowing.
IC Description
(1) General Description