Crazy hands - Open technologies: replacing K565RU5 with K555RU7.

 OPEN TECHNOLOGIES       
                                
        REPLACING K5b5RU5 WITH K5b5RU7.        
                                
(C) 1998 Master, VALEX, MAX     
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 1.Introduction.               
                                
   This article is intended for more or less
a knowledgeable public who knows how to keep pas-
drawer in hand and for which the computer circuit
tera is not a dark forest. We tried
We are going to do a detailed analysis of the technology
replacing handles to increase memory capacity
computer.  We have walked this path ourselves
a year ago without outside help.
When we encountered this problem, we
found that reference information or
none at all, or very few and without details.
Therefore, it was decided to share knowledge with the wider
some public. But the article is not intended to
plays the role of reference material, so
for noticed inaccuracies, please strictly
don't blame. In this article we will try
hang out in the provinces - after all, there are computers there
ditch in extension to 512 kilobyte practically
Honestly no. In our opinion, the expansion of the usual
new 48/128 KB computer up to
512Kb is the simplest and most logical due to its cheapness
visa and ease of modification. Ports, according to
which expands the memory to
512Kb, does not matter, althoughmost
the most logical and most accessible is the stan-
Dart Spectrum port 32765 (#7FFD)
by the sixth and seventh bits, which in
standard 128 KB Spectrum does not
are used.  It is precisely this expansion to
512Kb will avoid adding to the scheme
extra microcircuits. Moreover, it’s all the same
you will have to implement this port if you
remodel a 48Kb machine.  Prog-
frame support for the 512th expansion is already
has existed for a long time and continues to produce
to wonder.  The journal's policy is aimed at
support for this particular standard, but how
do everything at home - it's up to you to decide
discretion.  Back in the days of the USSR there were times
a great variety of spectra have been worked together
quiet computers that had large
schematic and ROM differences between
yourself. In order not to “offend” anyone, we decide
Is it possible not to “become attached” to some specific
linear computer diagram, and put everything in
in general terms.                             
                                
    2. Dynamic RAM on K5b5RU5/RU7.    
                                
   The ZX-Spectrum uses dynamic
RAM in the form of a line of eight chips
pieces for a 48Kb computer and
sixteen pieces for a 128 KB memory
responsibly.  They represent themselves
capacitor in rectangular package with
a bunch of legs.  They store information
represented as presence or absence
charge.  For stable operation of the handles it is necessary
you need to do recharging, called recharging
neration.  What is regeneration and why?
is she needed? Since the storage time is
series of capacitor is limited, it is necessary
We can periodically restore the charge.
This process is called regeneration, and
data recovery period - re-cycle
generation.  The table shows temporary
regeneration data for different handles.      
                                
       
            
            
            
            
            
            
            
            
            
                                
  3. Structure of the K5b5RU5 chip.      
                                
   The chip capacity is 64 Kbit, i.e. 65536
memory cells that are filled on the chip
talle in the form of a matrix of 256x256 points. For
reducing the number of addressable microphone inputs
circuit diagram, the cell address is entered in parts -
first the eight-bit address of the recording line
falls on the negative edge of the signal
RAS, and then the eight-bit column address
along the negative edge of the signal CAS in de-
row and column encoders respectively
from the multiplexer address register. De-
This will be discussed in detail below. In connection
with this feature of the RAM chip
has only eight address lines.        
                                
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
                                
  ***  - Регенерацию по этой ноге можно не
производить.                              
                                
   Матрица  микросхемы  разделена  на  две
части,  между половинками стоят усилители.
Так  что  каждый  столбец  состоит из двух
секций,  подключенных к разным плечам уси-
лителя.                                   
                                
      3.Принцип регенерации К5б5РУ5.      
                                
   Цикл  регенерации основывается на обра-
щении  к  ячейке памяти с периодом меньшим
или равнымTreg is restored
capacitance charge in the storage element.
The microcircuit is designed in such a way that
when accessing any cell in a row, the regis-
All cells in this row are blanked. When
each access to the matrix for reading
information is automatically carried out
regeneration of information in all cells of the pa-
memory belonging to the selected row. This
called automatic regeneration.
Therefore, in order to regenerate the entire
microcircuits are needed during the regeneration cycle -
tion to “iterate” all rows of the matrix, i.e.
access all rows of the matrix. If
access to different rows of the matrix occurs
walks with inter-
time shafts, then to automatic re-
neration cannot be relied upon and therefore
lead to forced regeneration. Existence
we consider the value of this type of regeneration
We will not revive due to complete unsuitability
for Spectrum.                            
                                
R.S. Stash from a barrel: due to the two-section
the onic structure of the microcircuit is not necessary
regenerate all lines
matrices (two sections are regenerated at the same time)
regularly), therefore it is sufficient in the cycle to regenerate
It's too slow to iterate through the first 128 rows of the matrix
tsy. Schematically it looks like this:
regeneration may not be possible for the last target leg
produce. A7 9 leg of the handle. Ifalong the way
eat your leg, then you'll lose pa-
mint and you can sign up for the love club
Lay colored squares.                  
                                
      4. Differences between K5b5RU7 and K5b5RU5.      
                                
   Chip capacity 256 Kbit - 262144
memory cells, which are made on crystal
talle in the form of a matrix of 512x512 cells,which in
four times the capacity of PYS. Therefore
used previously unused
the first leg of the microcircuit for additional
address A8. Otherwise, the microcircuits are completely
identical, which allows you to expand the RAM
computer without global rewiring
schemes.                                    
                                
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
                                
  *** - Regeneration along this leg is not possible
produce.                              
                                
  5. The principle of Spectrum RAM regeneration.   
                                
   In order to explain regeneration in
computer, we will have to consider non-
which things that directly concern
devices of the computer itself. According to some
it is known from unverified information that
the first computers Clive made
Sinclair, regeneration was done using
register R of the Z80 microprocessor. On the father-
high-quality Spectrum clones, everything is done according to
to another.  This honorable mission is entrusted to
video controller shoulders. Why him?
When resuming the screen with a period of 20 ms
the video controller reads the information from the
early area from addresses #4000...#SAFF. A
to carry out regeneration we need to re-
regularly read something from the RAM lines for
charge recovery. How can you miss
such a chance for "suspended" regeneration? Ka-
How this is done is discussed below.
                                
   As mentioned earlier, we need
we can redo the regeneration of RU7 microcircuits.
In order to do this, you need to find
the one who makes it.  This is what they do
address multiplexers. Take your diagram
computer and find the PYS line. By hell
in the tire of these hands (A0-A7) you will come
to the outputs of multiplexers. Usually this is KP11
or KP12. Multiplexers deal with two
important tasks:                         
                                
   1. Switching the address lines of the handles
for sequential processor access or
video controller, or rather its counters
Kam. When the video controller counters are running
gets the address of the screen memory cell
areas. After gaining access to the RAM, the
the deocontroller reads the value according to the
given address and thus we see
point on the screen.                          
                                
   2. Divides sixteen-bit addresses
processor and video controller into two parts
eight digits each. One "half" half-
The new address is written to the string register
PYS bynegative edge of the -RAS signal,
and the second - to the register of the PYS column by negation
to the significant edge of the -CAS signal. So about
all at once you get the full address in Russian
memory cells.                            
                                
  “What makes them click?” he will ask.
ordinary user. Multiplex work
sors are controlled by two signals. The first (called
all his N1) does what is described in
the first paragraph, and the second - respectively
the second point.  The second signal is usually RAS
or its derivative. Look at your diagram-
meh. Here it is necessary to mention the differences in the schemes
domestic spectroclones. There is due to
do different “polarities” of control signals
fishing  In some machines there is a control zero, in
others - one. Therefore, the H1 signal can
be active zero or one. Again-
look at the diagram. In this article, in order to
don’t get confused yourself and you won’t get headaches,
Let’s do this: active - one, pass -
siven - zero.  Based on this - a signal
H1=0, the processor has access to RAM, H1=1 -
access is open to the video controller. Second
signal RAS=1 (active) will be set for knobs
the so-called line. If RAS is zero -
it turns out to be a column.                       
                                
   For different combinations of control signals
cash (00,01,10,11) on the address legs of the handles
four signals are switched accordingly
la. Of these, two signals -from processor, two
signal - from the video controller. To make it easier
analysis of a specific multiplex circuit
weed block desirable all results
research summarized in a table similar to this
tsu:                                       
                                

















 * - additional address leg RU7.   
                                
   Here we should specifically mention the following:This is the signal that “hit” the table. This
H2 signal. When "drawing" an image onto
monitor screen video controller alternately
selects pixel values from RAM (by-
you) and attribute. "Adjustment" of this very
The above signal is rarely used. 
                                





 This is the so-called timing diagram
access to RAM. Repeated cyclically like this:
you are from the first to the fourth. In short, a signal
H1 is engaged in switching "processor -
video controller", and the H2 signal is responsible for
switching "pixel - attribute" during
operation of the video controller. But! During the
bots of each clock cycle are multiplexed
RAM access address using a signal
RAS.  Thus we have "row - table -
bets" (see the device of the handles).           
                                
   Now let’s connect all of the above to
table, namely - where and who in what co-
Does Lonke regenerate?                 
                                
   1. We found out what regeneration does
video controller, i.e. signal H1=1.        
                                
   2.Let us agree that regeneration is carried out
dim when the video controller reads pixels
screen memory of a computer that costs
on your desk and wants to become 512 kilos
byte coffin, i.e. signal H2=0. Why
exactly the pixel part of the screen? And so on-
it turns out safer, because to the attribute part
You may not be able to invest enough time into reading.   
                                
   3. It should be remembered that regeneration is
Rushka occurs in rows, i.e. RAS=1. 
                                
   At the “intersection” of all three conditions,
we get the column along which the re-
generation.  Now pay attention to
select the area in the signal table. This
and there is the combination we need. Everything is in it
signals must be pulsed. Conditional
but it is still necessary to switch
the lines we are trying to regenerate are
vat.  And yet - the repetition period of these signals
the catch should not exceed the regeneration period
tions of the memory chip (see Treg). All
fuss is contained in one small feature -
ness - if you “drag” some signal from
ligaments due to the fact that she doesn’t
suits you, then you need to pull his “sweet
a couple."  For example, if we change A0 and
A8, then we will have to exchange H3, V0 and
V6. If difficulties arise in the circuit design,
ok, then try the combination again
more   It all depends on the specific scheme
computer, so direct interference yes-
it is inappropriate. Circuit design given
transfer is carried out by soldering to
multiplexer (KP12) on the expansion board
RAM up to 512Kb from address A8.                
                                
   To carry out regeneration with additional
the lower leg of RU7 needs to move three
signal (for example, A8,V0,V6), which we
fit from the right side of the table into the column
for the "extra" leg of the RU7s in the lower left
parts of the table.  But then a new one arises
problem. on the expansion board we have KP12 and
it is controlled by RAS signals
and H1, but what about H2 and where to solder
signals V0, V6, when signal H1 is in
unit?  Let's try to figure it out
this situation.  There are two solutions, and
which one to choose - look at the specific ma-
tire and in a specific situation.             
                                
    First solution: through additional
logic elements. When the video is selected
controller by H1=1 we need through
signal H2 switch V0 or V6 in order to
screen we could see the pixel and the attribute. 
                                
    Second solution: this is through additional
telial exchanges (recrossings) in the table
tse tobish in the computer circuit.  For example
let's take the same signal V0, and we also agree
It was believed that the signals were A8 and V6. Collide-
we eat with the sameproblem. But in the left column
there are signals that are the same for all
bum state H2.  So in place of A8
we enter in the table any “double signal” (o-
identical for different states H2), and on
move the vacated space "triple"
signal (A8,V0, V6) from the right table. Te-
Now it turns out that for the finalization scheme
We enter, for example, A7 and V5. To the right half
wine, we will add new signals from the road map
boots A16 and A17, and in columns H2=0 and H2=1
Let's write "0" opposite these signals. Now
all that remains is to transfer all changes to the diagram
computer.                               
                                
    I personally (VALEX) want to say that in
both cases have their drawbacks. to you
you need to know your loved one’s circuit well and
dear "speccy" or resort to variation
antu: take your child to someone who knows, but not
so loved (or maybe not loved)
specialist.                              
                                
   Guys, let's live... on 512 KB!!!