piece of iron - "SPRINTER-97: Video System.

  First look at getting acquainted with your new computer is 
always throw on his screen. Well, maybe be the second, if never 
before seen "MiniTower" and AT-keyboard.



  (C) "Peters, 1997.



  In developing the video system computer
undergone significant changes. 16-color
screen submitted on the Enlight-96, remained in
distant past and at present from him was only the principle of 
switching the screen mode. 


           How to change the video mode?


  Concept: The screen is still split into familiarity 8x8 
pixels. In each familiarity defined its graphical mode. In each 
familiarity defined its mode output. Fullscreen is a block of 
1280-T familiarity - 40 familiarity across and 32 to

vertically.


              What are these modes?


  1. Standard ZX-Spectrum (ZX-40). In the familiarity of this 
mode is displayed in the normal character standard ZX-Spectrum 
- 8 bytes of the image and character 1 byte attributes.



  2. Mode ZX-80. In each familiarity are
two compressed horizontally standard characters
ZX-Spectrum. Conclusion pixels of these characters is made with 
a frequency of 14 MHz, which leads to increase the number of 
characters per line to eighty.



  3. Graphics Mode G256-7. Familiarity
is a graphical representation of 8x8
points, each of which may have any of the
256 and flowers, selected from a palette (16 million
colors).


  4. Graphics mode G16-14. Regime of high
permission. In each familiarity Horizontal
is 16 pixels, 16 colors per pixel. Vertical number of pixels 
remains equal to eight, and increases up to sixteen

only mode input INTERLIVE.


  5. Graphics mode G16-7. In fact, it
submode G256-7, which reduced the number of
colors per pixel to reduce the amount of video information.


    As the address information in familiarity?


  For the regime of ZX-40 all remains the same.
The shape and attribute located in a standard
ZX-Spectrum for all the familiarity.


  ZX-80. The first character - it's the same symbol that
and in the mode of ZX-40, the second - the symbol of the regime 
ZX-40 taken from the alternate screen.



  Graphic modes. In all three modes of address are identical. 
According to numerous requests programmers, and addressing of 
pixels has been changed. Horizontal pixels are solid mass in 
one video page, but vertical pixels are arranged in different 
video page. While it is possible location one page. It will be 
seen as alternative to the existing implementation.



  Addressing a familiarity in a way,
is a relative addressing. Specific
address of a pixel - the sum of addresses in the familiarity
screen and the pixel in the familiarity.


          How to address the familiarity?


  To determine the display mode requires three
bits of information. In the working version Sprinter'a
each familiarity has 2 bytes of information regime. Such an 
increase in the amount of information gives a fundamentally new 
opportunity. 12 bits Information videomode determine block 
address data from which to display information on

znakomesto.Takim this way, the question is about addressing the 
question of what kind of address recorded in this familiarity. 
This address determined by the system and user

program.


  The screen is made up of characters, chosen from a character 
generator, which occupies all space of video RAM. Number of 
characters (3072) exceeds the number of screen a familiarity

than doubled. This gives greater freedom to choose
graphic and symbolic images. In the
ZX-40 is the number of characters grows up
12288.


     Where is the information the video mode?


  For the video mode assigned to a special page
Video RAM size of 16 KB. These modes are a solid array of 
familiarity, which include the size of the area and zaekrannye 
5120 bytes to the screen. These visible occupy

2560 bytes.


  These data also contains some
Other information - the location of upper and lower human 
clock, the position of the curb, the beginnings and ends 
blanking interval, so the programming of this area will ROMs. 


  Opens a new opportunity. Now programmed timing signals to the 
TV / monitor that provides a simple way of hardware scrolling 
the entire image up, down, right and left. Changing the timing 
signals, You can change the position of general background on 
which and the battle will unfold a new byte SUPER-toys

for SPRINTER-97.


      How to use this expansion?


  In the G256-7, each pixel is
a single byte specifying the color of the pixel. Horizontal 
pixels are continuous array (320 bytes), which provides an easy 
way to writing data to the screen line by LDI / LDD-like 
commands. 


  Using superznakogeneratora, as a generator of images and 
control the withdrawal signs in screen mode by programming the 
familiarity dramatically accelerates when using a limited set 
of characters or graphic images. 


  Modes can be mixed! Mode of each familiarity is determined 
independently. His change does not require regime change

sweep, thus mixing there are no obstacles. Graphic Katrinka high
Permissions can be docked with simple graphics
Spectrum. This will provide additional opportunities
to accelerate such graphics programs, where
A familiarity enough to have two colors.


      As the page address of video RAM?


  It should be noted, the page of video RAM - this is
just a memory page size of 16 KB occupied by the
the needs of the video. Video page - this is the information 
displayed on the screen. 


  For the regime of G256-7 contains 80 video page
kB. In the standard ZX-Spectrum, it takes only 6.75 KB. The 
result - the number of video page ZX-Spectrum is much higher 
than number of graphic video page.



  An array of video RAM is shared by all modes, so the same 
information can displayed differently. Information for regimes

ZX-40 ZX-80, naturally, is not compatible with the information 
graphics modes, ie switching of the familiarity of the regime 
ZX-40 in graphics mode require a change in content Data of this 
familiarity. In order not to overwrite data after the switch, 
just use a different address data familiarity, written in a 
mode of familiarity. 


  Pages video RAM switched separately from the
pages of main RAM. Certain pages
main RAM projected on a video RAM. Record
in these pages is made simultaneously in both
RAM. Reading is made only from the main memory, which reduces 
the number of video RAM, and maximizes

processor speed (work with major
RAM does not require waiting cycles).


  What happens if I switch the page of video RAM and leave the 
old main page? 


  Information will go to the appropriate page
video RAM, and a former page of the main RAM
(Data from main memory to be overwritten).


  Switching page video RAM is
output to port address which will be issued
special functions of the ROM.


  What is the difference between addressing the data familiarity
between the graphical and ZX-40/80 regimes?


  Switching addressing video memory is
along with page numbers.


  Output to port address of the page the video RAM values 00h 
.. 3Fh connects different pages of the screen ZX-Spectrum. 
Values 40h .. 7Fh connect However, the video RAM, but with a 
different addressing mode. Values 80h .. BFh connect to the 
place of video RAM Page color palette. This is a separate page

size of 16 KB which is not included in 192 kBaytnoe
video RAM, but is addressed as well. Output to port
page video RAM value C0h .. FFh just
disables entry into the video RAM.


  WARNING! Switching data addressing
familiarity leads to a switch addressing
pages, because page number is part of the
addresses video RAM. Thus, a record in graphical mode full 
string length byte 400h will write data to a different page 
mode ZX-Spectrum. That is what prevents the specific binding of 
shadow pages of video RAM to the village core. They are 
switched independently from each other. 


  In addition, the addressing of pages of video RAM mode 
ZX-Sprectrum performed with 24 pages to 8 kB. In graphical mode 
pages are volume of 16 kb, and their number is sixteen.

Used only even-numbered pages of
range 40h .. 7Fh.

 16K x 16 = 256. Where did the extra 64K?


  Each row contains the graphical
400 bytes. They "stitch" through all 24 pages regime 
ZX-Sprectrum, and exciting in its quest additional 8 
non-existent pages. In fact, the record last 100h bytes of this 
string does not lead to entry into any cell of video RAM.



      What are the specific addresses of familiarity?


  For ZX-40/80 this same address screen, which
has the ZX-Sprectrum. All of familiarity on the extended screen 
is addressed in the same way, plus a video page address is 
changed. 


  In graphics modes, addressing different. All the video RAM is 
a set of 32 rows by 96 familiarity. Lines are related 
familiarity address resolution. Each such string represents a 
set of eight lines of 8h96 = 768 B, located in different pages 
of video RAM and have the same starting address. 


  Line familiarity are 2 groups of 16
lines. Data for each of the 16 rows in one group
are in the same pages of video RAM.


  All this information applies to a specific version of a 
working computer Sprinter-97. In the process further work may 
be some changes therefore, are not given a more accurate 
description addresses, ports, functions, ROM, etc.



       What are the possibilities of the new screen?


  1. The screen has everything to create a window system. In 
each window information can derive in its mode and these modes 
can be simultaneously coexist in a single window.



  2. Window has its own data area that can switch between them 
without losing information. Restriction is imposed only

total amount of video RAM. Suffice it to say
that the screen will have the opportunity to include
22 windows with a volume equal to the amount of information
on the screen ZX-Sprectrum.


  3. Random addressing information familiarity allows fast 
output homogeneous image, for example, background patterns 
("wallpaper"). For graphics mode it dramatically reduces the 
amount of output data. 


  Example: you take a repeating pattern of 256-color 16x16 
pixels on the screen 320h256 points. That in this case does IBM?

Draws this picture 320 times. But what makes
Sprinter? Draws a picture once, and then writes the address of 
the address screen image. So read speed image output at a much

lesser computer performance allows
significantly ahead of IBM in the schedule.


  Further, the question arises as to such screen
draw on, if the output of a small picture immediately propagate 
in all of its 320-Tee copies? The answer is very prost.V right 
place at the screen address changes to address output image.



  If you have a screen at least 40 familiarity
with repetitive images, the amount of printed information 
becomes equal to the total volume Information screen. If such 
familiarity more (and it is very common in programs), the 
information will be quickly decreases as the number of 
identical familiarity. 


  In addition, such a conclusion saves video RAM, which will 
increase the number of graphic windows with non-overlapping 
information. 


              On the color palette.


  The color palette Sprinter-97 increased to the maximum 
reasonable limit. Each color is chosen from a set of 16 million 
colors, defined by Data Palette RAM (24 bits / color).



  Palette - it's another whole page of RAM.
It is addressed similarly to other pages in memory, but has a 
completely different structure and appointment.


  Each color is determined by three bytes in
RAM palette. Each of these three bytes determine the weight of 
the blue, red and green in the defined color.