Animation on SPECTRUM - Most works on this topic begin with an explanation of what a pixel is, what an attribute is...

ANIMATION ON SPECTRUM'e  
                                
    Most works on this    
the topic begins with an explanation
what a pixel is, what
is an attribute... Let's start right away with
of what cartoons do
tion smooth.  Many noted
probably in some
animation programs more
smooth, and in some - less.
So, the movement of an object along
appears continuous on the screen and
smooth if it is synchronized
but with the frame rate of television
on-line image - 50 hertz
(or 50 half frames per second,
i.e.    25 full frames per
second).  On the computer exactly c
this frequency per processor
interrupt pulse arrives
(MI input). The easiest way
program synchronization, outputting
cabbage sprite on the screen, with impulse
interrupts, use this
processor command HALT, which
stops him before he arrives
pulse to input MI (Maskable
Interrupt - Maskable Interrupt-
tion).In BASIC the same effect
achieved by the PAUSE 1 command, but
creating animation on
BASIC is a thankless task,
Let's not consider this for now.
  If in your program you do not  
disabled command interruptions
DI, and did not turn on the second mode
interruptions, then for each
pulse MI processor accesses
program in ROM, execution of co-
which takes a certain amount of time
me.  When working with several
sprites, sometimes every beat
processor count, and so once
It’s not worth wasting his time
it. This is where the second one comes in handy
interrupt mode enabled by
mandoy IM 2, which is one way or another
otherwise used in almost all
game programs. In this mode
me address to which it is transmitted
control by MI signal, set
is arbitrary. At this address -
there may be a procedure
forming an image on the screen
not, or the RET command, ensuring
providing an immediate return to performance
the opinion of the team following the
mandoy HALT.                    
  Let's take a closer look  
correct activation of IM2 mode,
because are not implemented in SPECTRUM
all the features of this mode.
High byte of the table address, from
which will take the transition address
yes, according to the MI signal, must find
to be stored in the processor register I.
For example, let it be
number #5B:                      
LD A,#5BLD I,A                         
   The low byte of the address is taken  
c data bus.  Usually in a cycle
interrupt confirmation, it
may be equal to #FF, but full
guarantees that there won't be any
any other number, no. Therefore
the transition address can be taken
starting from #5B00 to #SBFF.  Yes
how can a number on a data bus
be both even and
odd, it is necessary that the table
the faces of the transitions consisted of one
nakovyte bytes, for example #FE.
Then, from any address in the range
zone #5B00-#SBFF can be taken
you two bytes #FE in a row, form-
interrupting service address
nia #FEFE.  Can be used
any address consisting of two
identical bytes (#8080, #CSCS
etc.).  Create a table
transitions can be done like this:            
LD HL,#5B00                    
LD DE,#5B01                    
LD BC,#0100                    
LD (HL),#FE ;program address byte 
              service ranges  
              interruptions.   
LDIR ;filling area 
              memory from 5B00 
              to SBFF by FE byte 
                                
     Second interrupt mode    
used not only for syn-
chronization of programs that display
screen sprites, but more on that later;
let's first figure out why
         sprite mask.