Opportunities Spectrum - A hardware scrolling on ZX Spectrum.

<b>Opportunities Spectrum</b> - A hardware scrolling on ZX Spectrum.

  I dug in ATM turbo 2 + nedokumentiro
bathroom seem - hardware scrolling. Feature
useful for games and the press and, unfortunately,
absent in almost all other models
ZX Spectrum. ATM2, GMX, Sprinter - here,
like, and the entire list of glands, where it is.

   Hardware scrolling on the ATM2 (draw
your attention: ATM1 anything like this
no!) is obtained due to the fact that the counters
raster and videoadresov separately, and in the text
Hilbert mode (as opposed to graphics)
counters videoadresov consider including
on the Border.

   Signal CROW (add 64 to the address) yn
ravlyaetsya through the multiplexer D64 (for signal
Nala RG2). Thus, at times,
if V2 <> B6, can naschelkat any address
divisible by 64. And to any naschelkat
address divisible by 8, to sacrifice
The upper 8 rows of the main screen (for
smear them in black): originally to include tech
Stove mode, and turn it to 0 .. 7 th
line. Remains the 192 line, which can be
use at their discretion.

   This is something I discovered purely random
chayno.Vo when editing documents
by V9990 I wanted to see what
firmware on the ATM2 (y HL8, and maybe a micro-
controller) should be replaced and that a further
done in hardware (transfer posting by
put in place HL8 other chips ...),
that appeared on the ATM2 hard to scroll
Ling. And it turned out that it is not necessary to change
Anything!

   This was followed (in a climate region
her privacy;)) febrile assembly
demonstration CATDEMO. The demonstration was
released in the form of puzzles - suggested
guess how it works effekt.Odnako guess
nobody could, from what I have concluded that
this feature or let developers
(Information about it has not lived in the form of rumors)
or simply was not known to them.

   Sources CATDEMO are on my website

      http://alonecoder.narod.ru/zx/
Suggest that we all want to use data
similar effect in their programs to take pieces
code from there, and here's why.


                    1.


   I set up makeshift evaporated. Pona
had made about two hundred intermediate
versions. As a result, setting a very ho
Roshi - nothing shakes, even if the interrupt
tion accounts for a very long time to
Mandu.


                    2.


   For this to work on future models
ATM, all the time-dependent pieces, ranging from
login hook, work in
non-turbo mode, and the rest of the program can
include a turbo.


                    3.


   In CATDEMO already provided (and used
form a) procedures to be considered
vat visible screen like a piece of a big car
Tinky, addressable by number the top visible
my line.


                    4.


   Support in emulators is simplified if
all programs will be used
the same piece of code. Potaktovaya emu
triangulation of all the glitches real hardware - it
very difficult and thankless task. For this
adequate model code looks like this
manner.

   Consider the display address (in the modes of
EGA, Multicolor, Text), consisting of an hour
 parts:

          000bS1 BMMMMM MMLLLLLL,
where:

   S - number of the screen;

   Bb - horizontal coordinate within
familiarity;

   LLLLLL - junior counters;

    MMMMMMM - senior counters.

  1. If text mode is enabled, then
early screen MMMMMMM = 0, then every 8 th
 string MMMMMMM + +.

  2. If enabled the graphics mode, the spacecraft
 zhduyu line MMMMMMMLLLLLL + = 40.

  3. If the Border shifted from the boundary
the crystallographic mode in a text, then MMMMMMM + +.

   The main screen (in the modes of EGA, Multico
lor, Text) begins at the 56 th line, after
INT. Line 224 cycles in non-turbo mode and
not less than 320 cycles in turbo mode.

   Text screen is shifted by one sign-
place to the right with respect to EGA / Multicolor
screen. I specify because, perhaps,
be able to use the upper 8 pixel
strings (which in the demo black) under the text
curves indicators TIME / LIVES / SCORE. If you use
use only a few of familiarity
these 8 rows, then it will not cost you about
tsessornogo time t.k.v this case, the conclusion
Information can be organized during the ve
rhnego Border, instead of delays.



   If during the flyback horizon
belorussian scan (except for transitions from string
Room 8x +7 on the line number 8x +8) include
text mode (to HR), and then turn off
(After HR), you can duplicate graphics
line. T.e.delat scaling the vertical
ticked or waves.


                  *


   To compile my ATM-IP-native
hodniki, you can put in UnrealSpeccy
del ATM 7.10 and connect a special firmware
ROM: glukatm.rom (in real life it would probably all
th, will not work because no initiation
induces memory loop - will then be corrected
Leno). This firmware in 48k BASIC
contains the procedures necessary to work
Driver memory ALASM (on disk with ALASM
this driver is called a boot).

   The same applies to a compile
Ball Quest for ATM. CATDEMO made on the basis
basis of the sources Ball Quest, so under the
gruzhaetsya a lot of extra modules. All that
relates to the subject of this article with a
is the main module CATDEMO.H.

Alone Coder