TPU 3035, TPU 3040
PRELIMINARY DATA SHEET
chained in 128-byte segments to avoid unused memory
space.
To present a WST level 2 display, the teletext display
controller has to evaluate the following attributes in par-
allel, that is for every character location:
– 10-bit character code
– 5-bit foreground color
– 5-bit background color
– 2-bit size
2.4. Display Page Generation
A stored teletext page cannot be displayed directly, be-
cause of the row-adaptive transmission and the level 2
enhancements (row 26–29). Therefore the CPU has to
generate a display page buffer, separated into level 1
datasuchascharactercodesandspacingattributesand
into level 2 data, such as character set extension and
non-spacing attributes. This is done by using a slightly
modified stack model, in which one pointer bit for every
character location indicates the presence of additional
parallelattributes. Fig. 2–2showstheorganizationofthe
stack row buffer. In this stack model the number of non-
spacing attributes per row is limited to 40, which agrees
with the WST and CEPT specification.
– 5-bit flash
– 1-bit invert
– 1-bit separated
– 1-bit conceal
– 1-bit underline
– 1-bit boxing/window
Additional attributes are defined to improve the display
of CAPTION and OSD text:
Level 2 Buffer
Pointer
Level 1 Buffer
– 1-bit italics
1
1
1
0
1
1
0
1
1
1
Char 3 Attr.
Char 3 Attr.
Char 3 Attr.
Char 3 Attr.
Char 6 Attr.
Char 6 Attr.
Char 6 Attr.
Char 10 Attr.
Char 10 Attr.
Char 10 Attr.
0
0
1
0
0
1
0
0
0
1
Char 1
Char 2
Char 3
Char 4
Char 5
Char 6
Char 7
Char 8
Char 9
Char 10
– 1-bit shadow
The display controller delivers 5-bit digital color informa-
tion, a shadow signal for contrast reduction and a fast
blank signal. The color bus can be used to address ex-
ternal color-look-up-tables (CLUT) which are part of
modern digital TV systems, such as the DIGIT 3000. By
this means, the full level 2 color spectrum can be dis-
played. For simple level 1 applications only 3 bits of the
color bus are converted into analog RGB signals on
chip.
2.6. Character Generator
Characters are displayed with a 10x10 pixel resolution
in PAL and 10x8 pixel resolution in NTSC mode. Pixel
clock is 10.125 MHz, derived from the main clock of
20.25 MHz. To get 10-bit pixel information two memory
cycles are needed. The character font is part of the
mask-programmable ROM, but supplied with its own
bus structure (see Fig. 4–1). By this means the data
transfer between character ROM and teletext display
controller does not stop the CPU, which is important in
the case of doubled line frequency.
0
0
0
0
0
Char 36 Attr.
1
0
0
0
0
Char 36
Char 37
Char 38
Char 39
Char 40
Fig. 2–2: Stack Row Buffer
Both bus structures are connected via a memory inter-
face which allows cross-connections using DMA or wait
cycles. As the number of addressable characters is
1024, the maximum character font size is 12800 byte. In
this case part of the character font can be shifted into the
program ROM which causes DMA cycles. Therefore
only less frequently used characters should be placed
into the program ROM. Vice versa seldom used CPU
code can be put into the character ROM.
2.5. WST Display Controller
The display controller includes two row buffers. The first
row buffer holds a copy of a teletext row from the display
page buffer. This decreases the data rate through the
DRAM interface by a factor of 10 or 8, because new tele-
text row data is needed only after 10 lines in PAL or 8
lines in NTSC mode. The second row buffer stores all
display attributes in parallel, to allow level 2 display with-
out additional decoding.
The WST specification defines a number of 7-bit code
tables, which are filled with 96 characters only. In the G0
code table some characters have several language de-
8
MICRONAS INTERMETALL
MICRONAS [ MICRONAS ]
