Buy or build the ZX Spectrum yourself? Easily! grmretro wrote in July 12, 2010
Moreover, another project is on the way - Speccy 2010. Progress has not bypassed spektrumistov, as they did not try to avoid it :-).
(photo of one of the prototypes. in the final version there are no wires for correcting errors)
You won't find a live Z-80 or a music coprocessor here. EVERYTHING IS INSIDE a large microcircuit and implemented in software.
Quote from the forum:
“The state of the software for today:
completely all the functions of Speccy2007 v1.06 (128k, pentagon makeshift, betadiska emulator, AY, tap / tzx / sna loading).
Besides
- - TV-out - RGB, s-video, composit
- - more correct and fast work with sna (now no dump bytes are corrupted)
- - turbo (7, 14 and 28 MHz)
- - weightless keyboard
- - all multicolor and bordereffects go clearly (like on a spectaculatore)
I plan to do more
- VGA in scandable mode
- mode with temporary houses of the proprietary spectrum
- kempston mouse and gluk rtc
- different modes with extended memory "
Speccy 2010 is also possible
DESCRIPTION OF THE COMPUTER CIRCUIT
X.X The structure and operation of the computer
The schematic diagram of the computer is shown in APPENDIX 4
(insert at the end of the book).
♦ CLOCK GENERATOR.
Assembled on elements D1 and D2. The frequency is set by the quartz
resonator at 14 MHz, and at outputs 5 and 6 of the counting trigger
D2.1, two antiphase series of half the size are generated
frequency. If you have a crystal for a frequency of 7 MHz, then use
By setting jumpers SA1 to the appropriate position, you can
exclude from the circuit the counting trigger on the element D2.1 and use
use antiphase signals from outputs 6 and 8 of the element
D1, following with the frequency of quartz.
♦ UNIT OF SYNCHRONIZATION AND TELEVISION FRAME FORMATION.
Signals of synchronization and formation of television
frame, as well as the control of the regeneration of the RAM are formed by the
from the signals at the outputs of the D3-D6 counters. At the exit
counter D3 generates signals NO, HI, H2 and NC. Invert
By detecting the HO signal, we obtain the CAS signal for clocking the micro
hem ram. RAS signal switching address multiplexers
D15, D16, is obtained by delaying the NO signal by one clock (you
stroke 9 of element D2). The inverted RAS signal is used to
clocking the processor. The "SCREEN" signal is a sign of a screen
area - serves to load shift registers D33, D41.
Signal "BORDER" - a sign of a border - loads into registers
gated multiplexers D30, 1) 31 color attributes boron
dera.
The signals at the outputs D3-D6 and flip-flops of the D8 microcircuit serve
to define line item numbers and line numbers in
frame. At the output of 3 elements D44, a line is generated
sync pulse SS. At the output of the 6th element D40,
vertical sync pulse KS with a frequency of 50 Hz. With the same hour-
This element D1 (output 10) generates an interrupt signal
IHT, according to which during the return path of the beam of the TV
kj> hviature and other input devices are polled.
The computer does not need to use quartz with a frequency of 14
(or 7) MHz. The synchronization circuit can be adjusted for an hour
This generator is quite wide. For this purpose
jumpers SA2 are designed, with which you can change the coefficient
counter recount D4. Enabling Preset Inputs
counter D4, depending on the frequency of the quartz is shown in the table
face on the computer diagram (see APPENDIX 4 (insert)). When
generator frequency, multiples of 500 kHz, it is possible to obtain
standard vertical sync frequency (50 Hz). If a
the frequency of your quartz is not a multiple of 500 kHz, then you need to set
jumpers to the position corresponding to the nearest specified in
frequency table. The sync stability of the TV is not
will suffer. Naturally, with a change in the frequency of the oscillator
the torus will change the speed of the computer, but this is not scary,
since when inputting from a magnetic tape, the computer is configured
to the repetition rate of the signals from the tape recorder.
♦ CENTRAL processor.
The basis of the computer is the Z80A processor - one of the most
powerful 8-bit processors, very popular for
abroad. Mass release of its domestic counterpart
1810ВМ80 - unfortunately, has not yet been established.
Registers D46, D47 play the role of address bus forming
drivers, and microcircuits D51, D52 form a bidirectional bus
data.
The functions of the system controller are performed by elements D14 (on
outputs 3 and 11 generate signals for accessing external
devices IORD - input, IOWR - output), D10 (outputs 10 and
13), D12 (outputs 3 and 6 RDROM signals - reading ROM and
CSRAM - access to RAM).
♦ PERMANENT STORAGE DEVICE.
Consists of two microcircuits of the K573RF4 type and has a volume of 16K
byte. It contains a monitor, a BASIC interpreter and a familiar
generator. In addition, there is a K573RF2 microcircuit, containing
which is a test program for checking a computer. Firmware codes TEST
ROMs are given in APPENDIX 1.
♦ OPERATIVE STORAGE DEVICE.
A 48K byte DRAM node includes
the actual memory chips D21-D28 type 565RU5, multi-
lexors D15-D19 of type 555KP11 and buffer register 555IR22
(D32). Here, the capacity of the 565RU5 microcircuits is not used half
ness, since the senior 16K bytes of the address space are
the assignee is assigned to read-only memory. Mul-
typelexers D15, D16 form addresses when accessing the process
litter to RAM, and D17-D19 - addresses of regeneration and access to e-
de-area of RAM.
♦ VIDEO SIGNAL FORMATION UNIT.
The video signal forming unit is assembled on shift re-
gates D33, D41 and D35, gated multiplexers D30,
D31, multiplexer D36, elements D11 (outputs 3, 6, 11),
D13 (output 11), D43 (output 12) and transistors VT4-VT10.
To shift register D33 at the end of the data access cycle
images on the SCR signal, this data is entered in parallel
code, and then issued in sequential code with frequent
that TI. At the end of the cycle of accessing the attribute data according to the
to the edge of the H2 signal into the internal registers of the multiplex
ditch D30, D31 attributes are entered. Shift register D35 for
holds the image data signal for a while between downloads
shift register D33 and loading internal registers
multiplexers D30, D31. When the beam is outside the boundaries of the
deopole registers of multiplexers D30, D31 are loaded from
second inputs with data coming from the border register
(D39). Switching the inputs of multiplexers D30, D31 controls
emits the "BORDER" signal
The final processing of the serial data code is
deo image is produced by element D11 (output 3). In the presence of
high level at output 12 of the multiplexer D31 at input 1
element D11 there are pulses of "blinking" "FLASH" from the output
11 counter D7. The input 2 of the D11 element receives a sequence
image data "VBYTE" from the output of the bias-
register D35. From output 3 of element D11, image data with
attribute "blinking" are fed to input 1 of the D36 microcircuit, control
By selecting the color of the point or the color of the field. At the entrance 15 of this
the same microcircuit receives a mixture of lowercase and personnel synchroim-
pulses from the element D11-11 (if a TV of type
UPIMTST) or from element D43-12 (for TV type ZUSTST).
Outputs 4, 7 and 9 of the D36 multiplexer generate a signal
piles of flowers. At the output 12 of this microcircuit,
signal designed to increase the brightness of color signals
cash, which is added with each color signal to
resistor-diode matrix (diodes VD5-VD7 and resistors R29-
R38). Then the video signals of chromaticity through the emitter repeats
bodies on transistors VT4-VT6 are fed to the "TV" connector. These
the same signals are summed on a resistor matrix (R42-R44), to
it adds the "SYHC" signal (a mixture of vertical and lowercase
sync pulses) through resistors R32, R41, and this mixture is
blunts to the emitter follower VT7, forming the "VIDEO" signal
for black and white TV. Moreover, each of the signals is color-
value is fed to the summation through resistors of different
minala to turn the color image into black and white
halftone.
Transistors VT8-VT10 generate inverted signals
R, G, B. Depending on the TV you are using, direct
or inverse signals R, G, B is carried out by jumpers
♦ OUTPUT PORT.
Made on a D39 (555TM9) microcircuit. Its ranks are Q2-Q4
determine the color of the border, category Q1 with the connected to it
RC filter (R24, R26, C12, C13) generates an output signal to
tape recorder, category Q0 - sound signal... Data to register
are recorded by the processor, that is, the border color signals that
the water to the tape recorder and the sound signal are generated by the program
Rammno.
♦ INPUT PORT.
Assembled on multiplexers D37, D38 type 555KP11 and working
melts as follows. Interrogation signals KA8-KA15 from address
processor buses through decoupling diodes VD11-VD18 and connector
■ "KEYBOARD" enter the keyboard and through a closed contact
the pressed key goes to one of the inputs of the D37 microcircuits or
D38 (in the form of signals KL0-KL4), whence, when a signal is present
IORD and low level on the address bus AO hits the bus
data. If the AO bit of the address bus is high,
then the signals from the joystick (DV0-DV4) and tape recorder are read
(TIN signal).
♦ NODE OF INPUT FROM A PHONE.
The input unit consists of an operational amplifier A1
(K140UD1208), acting as a limiter amplifier, and
comparator A2 (554SАЗ), which forms standard TTL levels
from the input signal.
X.2 Replacement of elements
♦ PROCESSOR.
Any Z80 processor or compatible with
him, for example, the U880 produced by the GDR. You just need to consider
that processors without letter index in designation
(Z80) are rated for clock speeds up to 2.5 MHz, so do not
all their copies will operate at the frequency of generator 14
MHz, although most will still work. In this case, you want to
It is necessary to set the generator frequency close to the minimum.
Processors Z80A, Z80B can be installed without restrictions.
♦ ROM CHIPS.
Instead of K573RF4 microcircuits, you can use K573RF6 or their
foreign analogue - ROM type 2764. In this case, the connection circuit
Will not change. As a last resort, instead of two K573RF4, you can
use eight microcircuits such as K573RF2 or K573RF5 (for
boundary analogue - 2716), including them according to the scheme shown in
fig. 1.1. Here, the 555ID7 decoder selects the desired
ROM chips. Of course, they will have to be mounted separately.
board by placing it next to the main board. At the same time,
the demand for addressable buses will increase and it is desirable that the tires
addresses were buffered. The current consumption will also increase.
There is another way to reduce the number of micronutrients in short supply.
roschem ROM. To do this, write to the K573RF2 microcircuit or
K573RF5 codes from the table of APPENDIX 3, and set atu mik-
the circuit diagram in place of ROMO, having first bend the output from it
21. Connect pin 21 to panel pin 28. Perform on
board changes shown in fig. 1.2. With bold lines you-
the newly introduced elements and links are divided, and the crossed out
ties must be severed.
A resident bootloader program will be written to the ROM.
After turning it on, it checks the RAM in the addresses O -
16384, where the operating system will be loaded later.
After completing the test, the screen displays:
Enter the "MONITOR-16K" program from the tape recorder (matches
with the contents of ROMO-ROM1, input time about 1.5 minutes), which
paradise will be loaded into addresses 0-16384 of RAM and there will be a salary
stupid. Further work does not differ from work with standard
new version of the ROM. You can work with all programs and returns
expand the OS with the "RESET" button. After turning off the power,
It is necessary to load "MONITOR-16K" again.
After such changes, other versions can be used.
OS, for example, with Russian font, etc.
♦ RAM CHART.
You can safely use 565RU5 microcircuits with indices B,
V, G. With microcircuits 565RU5D, difficulties may arise
due to their low performance. But you can try before-
beat the reliable operation of 565RU5D microcircuits, reducing the frequency
clock generator. Without changing the scheme, you can set
565RU7, connecting their terminals 1 with a common wire, but their capacity
will be used only by a quarter. In principle, it is possible
the use of microcircuits 565RU6, but they will need 32 pieces plus
additional decryption schemes similar to how it was
done when replacing 573RF4 with 573RF2. The design is obtained
cumbersome and complex, therefore, the scheme of such a refinement does not apply
is found.
♦ MICROCIRCUIT * SERIES 555 AND OTHER ELEMENTS.
All 555 series microcircuits can be changed without restrictions to
similar microcircuits of the 1533 series. Some may be
also replaced with 155 or 531 series microcircuits.
replacement of registers, multiplexers, counters and other micro
the circuit in the Zonov circuit on chips of the 155 and 531 series is limited
chen, mainly by the fact that their inputs are connected to outputs
memory or processor chips that have low
load capacity. Can be replaced on 531 and 155 series
multiplexers D17-D19 and D36, as well as counters D3-D6 and some
other logical microcircuits that do not load the processor buses
and RAM.
As for the D30-D33 microcircuits (according to the Zonov scheme), then their,
in principle, it can be replaced with microcircuits of the 531 series, but with
the condition that the outputs of the RAM microcircuits are loaded no more,
than one or two inputs of the 531 series microcircuit, and the rest
the microcircuits connected to them were from the 555 or 1533 series.
the same can be said about microcircuits that load the bus
cessor.
Register D32 can be replaced with 555IR23 by inverting
signal WRBUF at input 11, as provided in the proposed
scheme (jumper SA6). By functional purpose
register 555IR22 is completely similar to register 580IR82, but
unfortunately, the pinout differs and more
Energy consumption. Register 555IR9 in the Zonova scheme can be replaced
thread into two registers 555IR16, including it as in our scheme
(D33, D41). In both schemes, registers 555IR16 can be replaced
at 555IR1. There is no need to change the connection scheme.
In our circuit, as address bus drivers, you can
apply any microcircuits intended for this
(580IR82, 555AP4, etc.) in the corresponding inclusion, and in the
as a bi-directional buffer, data buses are ideal
microcircuits 555AP6, 580VA86. Counter 561IE10 can be replaced
on 555IE19 (the pinout is different!). Comparator 554S.AZ replacement
him on 521SAZ, which differs in the type of housing and the numbering of the output
dov. Operational amplifier 140UD1208 can be replaced by
140UD12 without changing the scheme, or at 140UD6 (140UD608), is
By using a resistor connected to pin 8. Transistors can be
put any of the series KT315, 312, 342, 3102.
11 / 11 829
print version
It just so happened that "Leningrad" was the very first Spectrum that I saw, and it was my first computer in general. Despite its simplicity and incompleteness, there are so many memories associated with this computer that I can't just forget about this Spectrum clone.
Leningrad was developed by Sergei Zonov in the late 80s. The boards are dated 1988 (ZS88):
There are boards dated 1989:
The computer is simple, contains a minimum number of microcircuits. The decryption of ports for reading is extremely simplified - all even ports are considered a keyboard port (254), all odd ports are considered a Kempston joystick port (31). This disgrace comes from the fact that only one bit of the address bus is used to decode ports - A0. An even greater disgrace is happening with the output ports, in particular with the #FE port - it is triggered when a value is written to any port at all, i.e. there is no decryption as such.
In addition to the "curve" of port decoding, the computer has a non-standard video output. This manifests itself when trying to connect it to TV tuners, PAL encoders and, in general, to modern LCD TVs. As a rule, such attempts end in nothing. This problem is solvable, I will talk about it a little later.
All the "Leningrads" I have seen are assembled in coffin-shaped cases. All jokes aside, the shape of the case with beveled corners is somewhat reminiscent of a coffin. In terms of dimensions, all cases are approximately the same, the only difference is in the material from which the case is made.
I will illustrate with examples:
This is all that remains of my very first computer. The case (by the way, quite massive for such a small size) is quite well preserved, and I still hope to collect the Spectrum in it.
There are also lighter aluminum housings:
This specimen is well preserved and has been restored. Looks like new now. Compared to the previous chassis, this complete computer weighs less than a steel chassis.
The third type of case is plastic. From my point of view, the worst case is:
Note the almost complete absence of blocking capacitors on the board. Despite this glaring drawback, the board has worked remarkably well for the previous owner for a good ten years.
If a toad choked a ready-made computer, then you could try to assemble "Leningrad" yourself, since it was not so difficult. I also soldered one "Leningrad" on my own when I was in my first year at the university. Then (in the mid-90s) it was possible to buy an empty "Leningrad" board on the radio market for ridiculous money without any problems:
Such boards differed in one feature - somewhere in the area of the tape driver, they had a short circuit of the + 5V and GND power buses. If during the assembly of the computer the corresponding jumper was not cut, then at the first turn on there was a great chance of getting puffs of smoke with one or more printed tracks on the board burnt out in a random place. Fortunately, I knew about this feature, and rang the bell in time and eliminated the short circuit.
In the same place on the market were sold computer circuits, microcircuits, keyboards, cases. In short, then there was a real paradise for assembling such structures. By the way, about the keyboards: the buttons from the microcalculators were mainly used:
The photo shows the old lettering on the keys with peeled stickers. These are clearly buttons from some kind of calculator. In terms of the quality of work and reliability, such keyboards did not stand up to any criticism. Maybe for calculators such shitty buttons are fine, but for a computer they are not at all suitable. Especially for games. I remember I hesitated to bend the contacts in such buttons so that they somehow worked. Perhaps the only positive thing about these buttons is their cheapness and availability. Therefore, at the first opportunity, I switched to reed keys, which were much more convenient to work with:
It turns out there were such "Leningrads" - with a built-in keyboard and a system connector. The scheme of this "Leningrad" almost completely coincides with the canonical scheme. The exceptions are tape input, beeper output and video output. The decoding of the #FE port in this clone has been corrected compared to the original "Leningrad" - the port is addressed at A0 = 0, unlike the original, where outputting a value to any port will trigger the #FE port. I launched the board. The photo of the board in the lower right corner on the breadboard has been modified to connect to a PAL encoder.
The board is generally well done - competent power distribution, space for blocking capacitors. I like it.
Unfortunately, it was not possible to identify the name of this clone (in the sense of the factory brand of the computer). There was only one inscription on the board - ЛС10.102.002.
"For 8 years I played Spectrum in black and white and you all know why, because our valiant TVs did not understand the RGB signal at all." I would like to say, ponstolg, remember that before the sun was brighter and the grass is greener. But I will not say, in my childhood no one ever uttered the word Spectrum. All my childhood I played dandy, later in sega, sometimes with friends in supernintendo. Neither in Dandy's program "New Reality", nor in "From the Screw", nor in any magazine, have I heard about this computer. I had heard out of my ears about computers booting from cassettes, but I had never seen them or knew their names. For the first time I found out about it only when I got the Internet. I read the forums, envied those people who in the late 80s and early 90s assembled their own computers, but I missed the suitability. Although in those years I was small and with all my desire I would not have assembled my clone of the Spectrum. How much have I lost? This is the question I started asking myself not so long ago. A year ago I came across a very good vidosik where one guy told in great detail and showed how to solder a clone of the Spectrum "Leningrad". I reviewed it more than once and in the end I decided “I will build my computer from scratch!”.
I decided to take the original scheme of Leningrad from sblive.narod.ru as a basis. Well, and add a bunch of improvements, such as adjusting the drawing of a circle (it is not clear how Zonov was able to design a computer with such a fierce jamb. It is expressed in font problems, graphics jambs, etc.), stabilization of a crystal oscillator, stabilization of frame and line synchronization, revision of the INT signal, introduction of binding to black level.
To make this process even cooler and more interesting, I did not look for a ready-made board, I ordered myself a breadboard rather compact size 12 * 18. I also had to order microcircuits and other small things from aliexpress and CHIPiDIP. The memory and processor had to be removed from a non-working clone, which I recently received from one spektrumista. I still don't know what kind of clone it is, there is no circuit for it, and I just dropped the microcircuits from it.
I decided to put all the microcircuits on sockets for quick replacement if something goes wrong. But the Spectrum contains a ROM, and it still needs to be flashed, I did not have a programmer, but the world is not without good people. Instead of two EPROMs, I decided to put one EEPROM W27C512, into which I sewed 48k basic, 128k basic, TR-DOS and a memory test for 48k, it is also nice to be able to switch memory banks with jumpers. But now all my details came, having thought in advance where which socket would stand, and began to solder them. Well, I stuck stickers on the board with the inscriptions where is the microcircuit and the numbers of the legs, which made my life much easier in the future.
Spending a couple of hours a day for two and a half weeks, I still collected it. I couldn't wait to connect it right away. And after turning it on, I saw White screen, which I already thought quite well. After rechecking the entire board, removing a couple of jambs, the situation did not improve. For a long time I could not understand what was the matter, but then I learned that you should not interfere with CMOS and TTL microcircuits. Yes, I'm that radio amateur. I had to order parts again and wait. After replacing all CMOS microcircuits with TTL, the coveted inscription still appeared, but the image floated.
Contacting the zx-pk.ru forum made it partly understand what was happening, but I had no solution. As a result, I had to sit for hours on the diagram. And voila, I just misunderstood the scheme for finalizing the formation of the INT signal, or rather, at first I understood it correctly, and then I thought what was wrong and did it with the jamb. Well, another problem has been fixed. But not everything is as rosy as we would like, frames were constantly running on my multimedia monitor. And then I decided to connect with the good old SHARP TV, which never let me down. But the truth is in b / w, since there is no RGB scart in it. And the picture on it hardly twitched. Again, an appeal to the forum gave good advice, to make a filter for a switching power supply.
And finally, the picture is normal, no twitching, we run the memory test.
But Spectrum also needs a keyboard. Then I got out pretty original, took old keyboard, pulled out a film with contacts from it, cut the getinax into pieces, soldered contacts on it, processed them with a file and glued them with hot melt glue to the keyboard, well, and soldered them according to the scheme. The result is a rather bulky external keyboard. Well, ports for Sinclair joysticks are built right into the keyboard. Joysticks from the sega master systems or atari are suitable, well, or, as in my case, a Segovian joystick soldered inside, for which I brought out the spacebar (namely, it is almost always used as an additional one) to the A button, well, when you press the C button, pressing up is duplicated, which is handy in platformers.
With the speaker, I somehow did not work out and I just brought the beeper to the TV, so at least the volume can be adjusted. Having written a simple melody in BASIC, having tested the sound, I decided to load some kind of game. And ... nothing worked for me. I assembled a tape reader on K554SA3, tried several microcircuits, rechecked the whole circuit, but it did not start, why, it is still not clear. I rebuilt the reader on 561LN2 according to the scheme from the Pentagon-48 (first on a breadboard before soldering) and everything worked the first time. Although the games were loaded, most hung right away, in some like DIZZY 5 it was possible to play a little.
Once, somehow, waking up in the morning, I wondered if I soldered the correct capacitors ... and OMG, instead of 47 nanofarads, I soldered 47 picofarads, and I also wanted something to work. Once again we order the missing parts, we are waiting. After the global soldering of the capacitors, you can finally play normally, nothing else hangs. I had to reassure myself that most of the games on the Spectrum are monochrome anyway, and I don't lose so much, that in the late 80s not everyone had color TVs and many played it with a black and white picture. But it didn't help much, you know.
And on my LCD monitor, the frames were still running. As a result, I still decided to solder an additional microcircuit to shorten the horizontal sync pulse, which I wanted to put at the beginning of the assembly, but for some reason I decided to save some money. As a result, I finally got a good color picture.
The image is really a little double. I checked it on the LCD TV, I can't see double vision. The picture is excellent. Super! But there is still free space on my board and it would be foolish not to use it. It would be great to do a memory expansion up to 128k and play 2015 castvania. To do this, we will change our K565RU5 to K565RU7 or an analogue of MN41256-08, which can be bought on aliexpress without any problems. By adding 7 more microcircuits, including the YM2149F sound chip, the board was completely filled. There were no problems with the memory upgrade. I expanded the memory up to 256k according to this scheme, but still I use it in 128k mode.
In the end, it turned out like this
Initially, I was not going to use the board on the table and for this I picked up a case from an old TV-box, theoretically you can put an additional drive controller board there on the second floor, but I don't want to bother with this yet.
The spec games turned out to be fierce hardcore, I only managed to get through the recently released Mighty Final Fight.
How much did I lose because of the absence of this computer as a child? In terms of games, it's unlikely, although the ability to rewrite games from cassette to cassette would be very much to my liking. In terms of programming in BASIC, it would hardly have interested me at that time.