Iron - connecting the "ALEGRO" (C-DOS) modem to the Spectrum.

(C) E. Milun (PAUL ATRIDES).               
                                          
   Connecting the ALEGRO modem (C-DOS).   
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 And now, dear  our readers, we
We'll tell you  how to connect a modem
"ALEGRO" to your computer. Since in
among the people  its other
name - "C-DOS", then in the future I will
stick to it.                       
  For  beginning,  I will confirm  statements
to all famous state ironworker
podina Kirill Gromov - co Scorpion C-
DOS  modem  does not  work. (Oh, don't bother
Guess it _now_ works. About how this
achieve - below.) But...                   
  But,  Scorpion is not to blame for this,
as this gentleman claims, and... himself C-
DOS. And it does not work not only on Scor-
pion'ah, but and on any computer where
implemented  normal  port #FF.        
                                          
                                          
  Why is this happening? Let's re-
Let's take it. Any externaldevice, at least
any  claiming this title
"external",  during its operation, it must
to the computer: “I started working, but
to  all internal ports, please do not
worry."  In a word - external device
triple should tell the computer that
it “cut through” the appeal to itself. It's clear ?
Well, C-DOS doesn't_do this.      
                                          
  Now let's look at everything in more detail. So,
computer  tried to contact to the port
#FFEF (port C-DOS) and immediately received an answer
immediately  from two devices: from C-DOS itself,
and from the internal port #FF. This happens
as follows. When reading the modem port
on  bus addresses appears address  #FFEF
(llllllll  lllOllll), since decryption
port  of the modem is carried out using only
one  signal A4, which is now at 0, then
C-DOS, naturally, is filled with
adequacy and begins to busily display the data
data bus. Everything is right, everything is wrong
is it? This is where it breaks into this idyll
in the most  arrogant  way Scorpio port
#FF. This  "disgusting" port to the same
the most  data bus, at the same time
begins to produce its own data.
That's it here we are! Overlapping with data from
modem, the attributes  distort them. Nothing
processor suspecting  about this conflict
takes its byte and tries to interpret
transfer  it as information received from
miracle of modern technology - the modem. And, es-
Naturally, nothing works for him!  
  Like-minded people K. Gromova at this moment
They rub their hands joyfully and say gloatingly:
"Yeah,  and we told you, we warned you. This
implementation  #FF -  incorrect, buggy.
Do it like we do."                  
  Here  here comes the time for us to intervene
and  say"Wait a minute, let's figure it out-
xya". Attribute port decryption occurs
according to all the rules of "good manners" - taking into account -
there is signal IORQ  (access to ports),
DOS (access to TR-DOS ports), as well as
state  4  address signals A0, Al,
A2, AS. So what's wrong here?
Signals  A0-A3  and  AS-A7 in 1st place,IORQ - in
zero,  because  there is a port request, DOS - at 1
because This is not a TR-DOS port. Not only that,
signal  IORQGE  (internal sampling resolution
early  ports) also inzero !!! And what, in
yours, should  "think"  #FF, if it
A completely normal request for him?        
  Of course, you can get into port decryption
that  attributes  signal  A4, but where is the guarantee
that when connecting any other
go devices you will not need a factory
put there A3, A6, A7, in short, don’t do it
FULL  decryption? There is another option
-  do not connect the #FF signal to portIORQ (as
and  is proposed by Mr. K. Gromov), but then
 another  problem occurs which we are talking about
wrote   in  first  our  number,  -  this
more   not a port  attributes,  because  naru-
 synchronization  connection work is progressing
processor  -  port  attributes", i.e.  sometimes
Garbage will be read instead of attributes.    
  Isn’t it easier to use a similar
Borrowing the attributes port "to the fullest."
And  you just need to do it so that outside
shneedevice, in this case a modem,
generated  signal IORQGE ? And since
signals IORQ and IORQGE are interconnected,  then
the appearance of 1st on IORQGE will lead to
that IORQ will also be set to 1,  and  you-
Borka  port attributes will not occur. By-
my,   this more normal  method.
 Let me remind you that  that such "glitches with the modem"
will  occur not only in Scorpion,
but and in any other computer in which
port #FF  implemented  completely,  not by
Gromov's scheme.                            
  But,  enough theories. To the point. We need to
press  C-DOS  generate signal IORQGE,
just and tells the computer, more precisely,
all its internal ports when they can
when to work, and when should they “shut up”
(IORQGE=0 - working  internal  ports,
IORQGE=l   - ports on the external device).
On  Scorpion such a signal is alreadyturned on
system connector. If on your computer
There is no such  signal,  then don’t despair,
to implement it you will need a small
what a piece  wires and... one resistor, but
about  this below (moreover, the signal IORQGE at-
Suitable for you not only for a modem).        
                                          
                                          
  So, here scheme for finalizing the C-DOS modem
(which,  naturally, must be inserted into
three modems) to formIORQGE. Scheme
ma  connected in parallel with the "standard"
connection of the modem.                 
                                          
                                          
                                          
           
            
            
            
            
            
            
            
            
            
            
            
            
                                          
  Транзисторы - KT36l, KT3lS или им подоб-
ные,  буква  значения не имеет. Микросхема
DDl - типа ЛЕl, любой серии lSS, SSS, S31,
lSЗЗ или любая другая микросхема, содержа-
щая логические элементы 2ИЛИ-НЕ, нужно то-
лько учитыватьposition of the legs.        
  Signals  A4, IORQare taken from the system
connector there  same  starts  and IORQGE.
Moreover, A4 and IORQ are already being brought into fashion
mu  (in Scorpio - contacts 24V and 17A system
dark connector, respectively), i.e. to you
in fact  need will be  add  only
IORQGE (in Scorpio - pin 13V).      
                                          
 If youstill not satisfied with the choice -
as  modem  by  one  signal A4 and/or
The diagram given to you above does not give the
living  result, then you can use
call for a more complete decoding:           
                                          
   
   
   
   
   
   
   
   
   
 How  see,  need just addone
microcircuit DD2, containing at least three
element 2AND-NOT, for example LA9  series SSS,
lSЗЗ, lSS. DDl - the same as in the previous one
scheme  (to form IORQGE). Total
for normalconnection and decryption
modem  you will need only two micro-
schemes - LEl and LA9.                        
  Signals  A0,  Al, A2, AS, DOS are taken from
system  connector (for Scorpio - con-
bars  9V,  10V, 11V, 23V, 4V), and are
the very same ones for which in Scorpio the
goes  decryption  port  attributes. When
this the modem will  response to any
port,  address  which in binary
represents   number  хххххххх
xl0xlll, and is not  a TR-DOS port. 
If you signal DOS  not  displayed on
system  connector  and you don'tknow where it is
take  then  instead of  him you can start,
for example,  A6,  A7, ...,  or even just
supply  +5V. In principle, this should not
on  which affects  because ports TRDOS with
similar addresses  - no. Signal A4 - that
well,  that  originally  was summed up  kmodem, i.e. taken from the system connector,
or from the connector on the modem. Last option
preferable.                         
  The resulting  signal  MOD is set to
modem (and into the formation circuit IORQGE, co-
which  is now part of the modem) instead of A4, that-
there track A4 on the modem is cut with
the part that is connected to the computer
rum, is taken  A4, and is brought to the other  
MOD.  This is shown in the following figure: 
                                          
                                          
      A4, from gap       A4, к     
    компьютера                  модему    
    ■■■■■■■■■┬■■■■■■■х■■■■■┬■■■■■■■■■■    
             │             │              
             │             │              
       A4, к схеме    MOD, от схемы      
       дешифрации     дешифрации          
  Теперь о том, как сделать сигнал IORQGE
в  других  компьютерах.                   
                                          
        Схема проста до идиотизма:        
                                          
 signal IORQGE  560 Ohm  signal IORQ   
  ■■■■■■■■■■■■ ■■■■■■▓▓▓▓■■■■■■■■■■■■■■■   
(system connector)  (20 leg Z80)   
                                          
  Signal IORQGE  output to the system
connector  (for example,  v  Scorpio is 13V in
60pin connector), and the signalIORQ
connects directly to the microprocessor
quarrel (to the path, of course). That's it, now
You can connect to  your computer
refrigerator. And if it arrives at the right time,
cops  inform the computer about your work
Bot, then everything will be “hockey”.              
                                          
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