Iron - memory expansion for Tashkent-128.

╔──────────────────────────╗
      │ 3. MEMORY EXPANSION FOR │▐
      │ TASHKENT-128 │▐
      ╚──────────────────────────╝▐
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 From the editor:
  Finally, it's done!  Now the user
The Tashkent version of SPECTRUM can  
gain access to the software
niyu, for which work requires more 
128K RAM. Moreover,
Recently there have been more such programs
noticeably more.

 This diagram is based on the diagrams
computer improvements proposed in
electronic magazine SPECTROFON
(N17,18). Since these improvements
compiled for the PENTAGON-128 computer
,then directly apply them to PC
TASHKENT-128 is impossible.
 Changes in the scheme taking into account features
PC TASHKENT-128:

 1. Changed the order of connecting signals
computer to additional
multiplexer control circuit RAM 512K
K5SSKP12.
 2. Decoder K5SSID7 with 6 diodes
log replaced  circuit on IC LL1 and LAZ,
using the computer's C-#FD signal.

 The control board serves port #7FFD
in PENTAGON mode and ports #FDFD,#DFFD in
PROFI-ATM mode.
 When switching to 48 K mode, the circuit
blocked while maintaining the bank number
RAM.
 The control circuit is implemented on
separate double-sided board, drawing
which is given in the appendix.
 The electrical circuit diagram is not
is givendue to the complexity of its input (
if necessary it can be
restored from the printed drawing
boards).
 To implement the scheme you will need the following ICs:
K555LAZ, K5SSLL1, K5SSKP11, K5SSKP12,
K5SSTM2, K5SSLE1 (6 cases in total)
-, for control board;
16 memory chips K5b5RU7 (
recommended with the letters B, I, K and better
[SP-FON17]) - for implementing RAM 512
KB.
 It is better to connect 512K in
two stages:
 1. Replacement of memory IC and troubleshooting
damage on the computer board,
arising during this operation.
 2. Assembling and installing the control board
followed by debugging.

            ─────══════─────  

 REPLACING MEMORY ICs is the most dangerous (for PCs)
surgery, so it is necessary
carry out with extreme caution. Not
be too lazy to choose a convenient tool.
The IC can be removed using a soldering iron with
long, single-row tip (with
In this case, try to heat up places less
soldering and raise a number of IC pins from
first time), alternately unsoldering the 1st and
2nd row of the microcircuit.  You can get by
by biting the IC, removing the remaining ones
part of the pins on the board with a soldering iron (in this
case, remote ICs will not be possible
use further...)
 After removing the IC, carefully
inspect the PC board and eliminate any problems
when removing the IC, parasitic connections (with
In this case, beware of deleting necessary
connections).Install the RU7 IC instead of the remote ones, if
In this case, do not heat the IC terminals any more
2-Zsec (it is advisable to power the soldering iron
via power regulator or via LATR)
 Combine the 1st pins of all RU7s into one
tire (it is better to use a mounted
installation) and temporarily ground.
 Connect the RAS line via resistor 1
kOhm to the +5V power bus (3rd pin of IC LN1
to the right of the quartz resonator).
 After checking all circuits of the RAM block with a tester,
turn on the computer. On the screen, after
passing the initial SOS test, must
the SPECTRUM-128 menu appears.   When
if the test fails, try connecting
RAS line 4th pin RU7 through capacitance
47-240 pf with ground (carefully). Possible
you will have to increase the capacity or number
blocking capacitors near the IC
memory.
 After a successful test, 128K RAM is available
all even pages of which are not
are regenerated (cause of failures during
trying to enter a program in BASIC or
load from disk; give the CLEAR command
32767).Try to make friends with different
programs (for example RAM test, some
of these will show OK.).
Performance (partial possible)
parts of the software indicate serviceability
block of RAM.

            ─────══════───── 

    CONNECTING THE 512K CONTROL CIRCUIT

 Assemble the control board according to the drawing
given in the appendix.   Before
be sure to check the IC installation
fee forshort circuit of conductors between
yourself.
 Purpose of BOARD and computer signals:

STROBE - write signal to ports #XXFD
PORT - select ports #7FFD or #FDFD, 
       #DFFD
D0, D1, D6, D7 - CPU data bus lines
A8, A9, A13, A14, A15 - the same name 
CPU address bus lines
A8' - served instead of A8
CPU - CPU access to RAM (CPU=0)
L/H - selection of high/low part
RAM addresses
B14 - video controller signal
RAM - line connected to the 1st pin. RU7
RES - reset
BLOCK - shutdown 512K
 Necessary changes on the board
swap computers:

     DD20(11v) <──> DD22(6v)
     DD21(11v) <──> DD23(6v)
     DD22(13v) <──> A8'(control board)
0 ─> DD23(13v) ───> B14(control board)
     DD26(1v) <──> DD26(4v)

 Location of signals on the PC board

     STROBE - DD26(8v)
     RES - DD25(1v)
     A14 - DD27(13v)
     A15 - DD27(12v)
     CPU - DD22(15v)
     L/H - DD22(1v)
     RAM - RU7 (1v)

 PORT,BLOCK output to the connector
keyboards having previously separated 2
terminals with an awl from a common bus.
 The remaining signals are removed from the ROM IC
(since many boards have 4 ROM ICs, 8 each
KB replaced by one capacity 32
KB, then you can output signals from
free holes)

            ┌────┐ ┌────┐ │2│ ┌────┐
            │ │ │DD27│ │5│ │DD26│
┌─┐ ┌─┐ └────┘ └────┘ └─┘ └────┘
│D│ │D│ ┌─────┐
│2│ │2││ │
│1│ │0│ │ │
└─┘ └─┘ PLACE │ │
┌─┐ ┌─┐ INSTALLATIONS │ ROM │
│D│ │D│ BOARDS │ │
│2│ │2│ CONTROLS │ │
│3│ │2│ │ │
└─┘ └─┘ └─────┘
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