(c) DANGEROUS
(c)LD
ZX-BUS IS REAL ???
Computer experts - something like
consultants for computer tailors.
You are making a computer system for yourself,
and they give you advice in absentia on how to sew.
Not an ideal method, but still the best
better than nothing.
The problem is that the computer
a tailor, as a rule, sews his own
topic once in a lifetime, so no experience
whom. (This applies primarily to
"tailoring" a computer-based system
ZX-SPECTRUM). Owners of other computers
thorny platforms (a classic example is
IBM) have any kind of support in vi-
of all kinds of watery literature,
and the main thing - in the form of cones and devastated
the pockets of your friends and acquaintances.
This means there is a chance not to repeat their mistakes -
ki.
For spektrumists everything is much more complicated.
The apparent simplicity of Sinclair iron
extremely deceptive. After all, after all,
It's computer technology after all!
Therefore, the unfortunate tailor very boldly entered
Buries inside his computer with a needle
some thread (that is, with a soldering iron and pro-
waters) and carefreesews only
that you bought a sleeve for your jacket.
Hooray! The sleeve is sewn on! Even, like, a hand
fits in. Now there's a little more left
push yourself and save some money at least
on the second sleeve. A little time passes
no, and now - the second sleeve is in place... What
is that? For some reason, the hand
the feather doesn't fit into the first sleeve?! After all, he
sewn correctly!!! So, now
we are... We rip off sleeve number two. All
great, my hand fits into the first one again
sleeve. We begin to suspect that the second
The sleeve is somehow wrong. What if
should I sew a second one in place of the first sleeve?
Wow, the second sleeve fits! So
We will sew the first sleeve in place
second. There's trouble again, we won't interfere again
first sleeve. Ah! It’s clear, now
let's try all the combinations, maybe...
Anything will do! After a few
hours the unfortunate tailor, finally
exhausted and tangled in wires,
gives up, sadly thinking: “But I wanted
also some buttons and a tie..."
With a wild cry of "A-ah!!! Again, not half-
it happened!!!" the tailor tears off all the sleeves
"along with the meat" and loses his
jacket...
This is approximately how the connection happens.
reduction of peripheral devices to suppression
the vast majority of Spectrum models
portable computers. Comparison may
and not very successful, but the performance is yes-it is exhaustive.
It’s more pleasant to compare digging in the brain
computers with swimming in the lost
corners of the ocean. The user does not
believes that during the connection process
something extraordinary will happen. Here-
then the underwater ones begin to show themselves
stones, horned mines and depth charges
computer circuitry!
“How,” you say, “and the pilot, then
are there instructions for connecting?
Instructions are instructions, that's all
does not take into account the specific navigation area
niya and therefore will not show you
minefield maps. Instructions from the beginning
assumes that there are no mines and there will be
cannot, but the underwater rocks have long looked
vanished by those same bombs.
- What kind of paradise is this with sand-
a beautiful beach and crystal clear water? -
you ask.
- There is one! - we will answer you. -
This resort has a romantic name -
"Computer bus" They rest in it
happy owners of Spectrums with tires
new architecture and do not know problems with
connecting any peripherals
rial devices. A unhappy user
for those who want machines of the "in itself" class
the entrance there is simply closed.
The purpose of this article is to
to help users calculate
take space on your computer fromall sorts of things
unpredictable electronic-probability-
trash and create it in your own
Spectrum computer bus, but not
then a bus, but an absolutely buffered bus
according to all the rules of computer circuit design
nicknames
Technical digression.
Electronic probabilistic junk. Yeah, yeah
very mysterious definition unknown
what. And here it is, no one knows what, bolt-
resides on the computer unknown where, and therefore
moreover, it is unknown where it came from
elk... Let's try together step by step -
but to understand all this unknown -
tee.
Let's start with a simple logical reasoning -
Denia. What passes through the conductors of the internal
ri of our computer? Flows through them
electric current. "Well, it suits a hedgehog too."
It’s clear,” you say.
Just a minute. Let's first share the pro-
water workers for their intended purpose - for power and
signal.
Power is supplied through the power conductors
connection to the microcircuits, and therefore the current
great power flows through them. Signal
conductors are designed accordingly
name, for transmitting signals, roughly
speaking, from chip to chip. Strength
the current in them is orders of magnitude less, but notThis is the only thing signal wires are famous for -
nicknames! The current strength in them is not constant! She
changes chaotically, depending on
for example, a command executed by a process
rum, or periodically, for example, on
the output of some frequency divider.
If in the second case it is possible to fail
statistics and predict behavior
signal in the future, then in the first
what statistics are out of the question.
In short, combinations of signals have
those who relate to the transfer of information
(periodic signal no information)
does not carry) can accept the most
strange forms, from a primitive meander
to high duty cycle pulses. This is on-
places certain requirements on the
transmission of such unpredictable signals
catch
Let's move on.
If the current of the signal conductors depends
sits from time, then, let me tell you, where is he from?
is it taken? That's right, from the power supply circuits.
This means that the current strength in the power circuits is also
not permanent! And that's not all. Micro
circuit when switching from one state-
angling to another "misses" from the conductor
power supply to the ground is a significant current.
With all this, we must not forget that
that the power conductor has absolutely
specific resistance.
Now let's remember Ohm's law and
let's estimate the situation at the momentswitching
microcircuits. The supply current constantly changes
it turns out there is resistance in the circuit, it follows
Therefore, the supply voltage in the vicinity
the microcircuit under study will jump
in accordance with the logic of its operation, then
eat in sync with the information! Therefore ab-
absolutely real situation in which a number of
closely spaced microcircuits in one and
the same moment will require for itself "more
more nutrition."
What will happen? A that the tension
power supply in a given area for an instant
the value will drop so much that it can easily
can disrupt the work of not only these
microcircuits, but also “not guilty of anything”
neighboring ones.
If we think further, we can
come to a sensational conclusion:
if a failure occurs during transmission
some specific information, then computer
The yuter will always crash this month -
those!!! And this means that on a specific
computer instance may easily not
go to a specific program! you will
test RAM a million times, check
data bus stability and reliability
rations and you won’t get any results!
Here is a description of the most harmless and
an easily eliminated glitch called
"rubbish nutrition". Fight it
trivial, between power and ground buses
in rows and columns the so-called
called "blocking capacitors". Zarya-
huddlingfrom power circuits, they give off micro-
rocircuits their energy in those moments when
Yes, the latter are “starving”. Also, for the purpose
reduce resistance, apply
thick-thick (wide) conductors, according to
which supplies power to the microcircuits.
The classic "nutrition rubbish"
there is a mutant brother, but more on that in a moment
later.
Further worse. Let's move on to the signal pro-
water workers carrying information. Shape sig-
nala, as we found out above, is unpredictable
zable, the signal spectrum is also unpredictable
I eat. (Signal spectrum - frequency band, in
which the signal energy is transmitted to
this moment in time. Determination of the
primitive, but it works.) So,
the conductor is obliged to completely and completely re-
edit the spectrum, otherwise the signal shape may
change as you please. And short
impulse is much more difficult to convey than
long, since the short pulse
the spectrum is wider and, accordingly,
reaches higher frequencies. Scary
The biggest enemy of short pulses is capacitance.
conductor. She cuts down all high-hour
full spectrum component, while from
short clear impulse remains
"softie" with a small amplitude, which
also arrives late for delivery
how many nanoseconds, and the receiving chip
may easily not react at all to
"I'll be a mess." That's it, the computer hangs. But what sa-my sneaky thing is that this
the situation is often highly unlikely
character, and in one case out of a billion
it will arise. This manifests itself very
clear: Your computer once every two hours
freezes regularly for no apparent reason.
Naturally, you examine him for a long time,
looking for installation defects, complaining about the inconsistency
abundant food online and so on. Bess
useful - Your computer froze, moved
sags and will freeze. The nature of the movement
sanitary may vary depending on the surrounding temperature
temperature, humidity and other factors.
This disease is poorly treated if it is
wife in the design of the computer
tera.
If you yourself introduced the disease by soldering
wires to the periphery, then the treatment is simple -
unsolder it, and all problems will be solved by themselves
yourself. "They're bullying." - the reader will think -
tel. And in vain, because until the end of the article
It’s still a long way off, but the advice is to throw away the sealed
no new peripherals have been reported yet.
Let us continue the martyr's description of gluten
cov. The next one is classic, to say the least
Well, a textbook glitch - overload
data and address buses. It's no secret that
load capacity of the Z80 processor -
1 TTL input. In the computer itself, contrary to
documentation, poor processor is loaded
for three or four inputs, and if we in addition
solder a couple of pe-
peripheral cards yesLet's also turn on the mode
"turbo", then the processor will not show much -
xia, and your computer... well, you guessed it -
eating...
Every tire manufacturer
Spectrum-compatible cars, coming out
this situation using our own methods.
The company "Scorpio" produces an expander
buses with address buffer. Not the worst
solution - and quite cheap. Lack of
current is half measures, the data bus is still
absolutely not protected, and this despite very
"weak" in terms of loading method -
processor Z840006PSC, which,
in addition, it is designed to work on
frequencies of no more than six megahertz, and in
turbo mode works at seven.
Solves this problem in a completely different way
company "NEMO". No bus buffers
at all (why buffer addresses if
does the data go naked?), but the processor
powerful and expensive is used -
Z84C0010PEC , designed to operate on
frequencies up to 10 megahertz, in turbo mode
also taps at seven. Disadvantage -
expensive processor, unclear load limit
viscous ability when used in
computer "KAY", as well as complete
lack of buffers.
As you can see, each of the listed me-
Todov is not without its shortcomings.
The most painful place in the shaper
buses are a bidirectional data buffer.
This is what our computers are still ignoring.
new manufacturers. The reason, we suspect,
clear. Control unit design
requires very careful and responsible
nogo approach. After all, the processor should not
notice the presence of a data buffer, and
the buffer must switch perfectly synchronously
start your direction in accordance with
requirements of the processor and peripherals, which
which he buffers, otherwise there is a conflict on
bus and complete system crash.
For a snack, we’ll present you with another gluten-
chok, the mutant brother of "trash in pi-
Tanya". This glitch has not yet been fully studied.
chen, as he recently appeared in the background
mass buffering. Let's imagine
situation: we have sampled the bus for
connecting peripheral devices, then
there are put in a gap in the tire powerful re-
signal carrier who is not interfered with
all sorts of wire capacitance, pickups and
etc. Our buffer is calmly and easily pro-
pumps the entire capacity of conductors and input
high capacity of peripheral cards.
What does pumping mean? Microcircuit in
moment of switching its output from one
logical state to the opposite
forcedrecharge the container, "hanging-
"at this output (printed conductors
ki, wires and what is connected
these conductors and wires - everything
has some, sometimes significant,
bone).
The recharging process looks like this:
let's say for some time
the output of the microcircuit was logical "zero",
or, physically, zero (almost) volts. This
means the load capacity is charged
to this very zero volts (simply
discharged). At some point in time
the microcircuit decides that it would be necessary to install
output a logical “one”,
in other words, about four volts. But
if an emitter is connected to the output of the microcircuit
bone, you will need to charge it first
it up to those same four volts, for which
it takes time, and only then can you
will say that the output is set-
there was a unit. The microcircuit wants to do
it's fast, and from her in the first moment
ment requires significant effort.
It is known that the faster it is necessary to
charge the capacitance, the greater the current for this
required. Modern microcircuits can
capable of delivering significant current to the load
- without a twinge of conscience they will take it away from
power source and will be sent to reboot
row of containers. So recharge
it just happens instantly.
If the load capacity of the buffer is large,
thenour buffer chip becomes
simply a wonderful source of interference
nutrition, which sometimes leads to complete
computer malfunction. But
for normal bus driver
three such microcircuits will need to be installed
pieces - two for addresses, one for data!
It turns out a vicious circle - unload
signal processor - creating interference
on nutrition, and vice versa. What to do?
The most ideal, but very impractical
solution to the problem - buy a second one
power supply specifically for three micro-
buffer circuits. The second way is to try
fight the “nutrition rubbish” with
power of blocking capacitors.
Very often this helps a lot, especially
especially with a small load capacity.
In addition to this, you should carefully select
conduct power circuits so that the main power
the chains went primarily to these
microcircuits.
Oh yes, another appetizer! Microcircuits
relatively new series (1533 and "fresh-
zhe"), having low input currents, not
carry long conductors, connect
to their inputs, which leads, primarily
first line on pulsed and asynchronous
inputs, to false positives. Under treatment
only by shortening long conductors.
Another method used by some
by amateurs - installation at inputs where
there is a hindrancesmall capacitors
bones. In our opinion, this method can
can only be used for operational purposes
identifying a glitch, but not for it
elimination. Capacitors located in the center
five digital signals - pornography,
speaking about the unprofessionalism of the creator
equipment or unfair approach
de to the development of a scheme and constructive
execution.
After such a terrible technical
digressions sometimes become unclear,
How do these same computers even work?
are they melting? Yes, they somehow work.
The phrase itself "I have a computer
works" every user perceives
swings in its own way. Some believe that if
the computer worked for at least half an hour without
hangs, then, in principle, everything is fine,
can be used. Others are in spirit
do not tolerate unauthorized failures in
work (we naturally consider ourselves to be
last).
Many former spektrumists left
Spectrum is not at all due to the fact that
childhood dreamed of another car, but from
hopelessness of fighting against numerous
failures, while observing the same situation
from their comrades. After which they often
the whole company is switching to another
platform, forgetting the Spectrum, how scary
dream. Reminding them of their existenceSpectrum (no matter which one) causes
them sarcastic (from their point of view)
laughter, completely idiotic from the point of view
niya "new spektrumist".
"New spektrumist", in our understanding -
nii is a person who has norms
small glitch-free Spectrum with bus
architecture, normal body (in which
everything is rationally arranged, and not
chock full of wires and boo-
spacers between the boards and the core
by the way... yes, by the way, a funny story!
One of our friends, having taken it for repairs, is right -
Yes, not the Spectrum, but Caller ID, having disassembled it,
found, as usual, a lined paper
ku, which, upon viewing, turned out to be
"Patient card"!), with a normal key-
ature (not necessarily from RS, but other
they simply don’t do it anymore), with a pulse block
power (not based on TN-180 and mountains
radiators), as well as all sorts of peripherals -
cards that he purchases
at our own discretion.
The old Spectrum is also forgotten, like a terrible
a dream, and the reminder of it causes
sympathy for the owners of such
machines, which, in turn, hourly
they don’t understand all the charm and beauty
bus architecture, looking for all sorts of
different arguments like "And I already have
everything works!”, soldering for the tenth time
wiring torn off from the board. Until then
since thenuntil... until they are forcibly poked
nose, like blind kittens in milk, and not
will show what it truly means "Everything
works!" When the Spectrum is on
can be turned over, placed on its side, and
nothing falls out of it,
and the computer itself does not reset, even
being turned on for two or three days! A
what a beautiful installation! A as co-
Peripherals stand well in the “mother” board
cards...
The "old" spektrumist, as a rule,
immediately admits to himself: “I want
the same!!!”, however, he doesn’t show it,
saying: “Well, yeah, basically nothing,
not bad.", soberly realizing that the Persian
the prospect of buying a similar computer
very vague for financial reasons.
He also realizes that over the past couple of years
manufacturers came up with so many
peripherals that ee connection will turn
his old Spectrum in Tumbleweeds.
However, we started chatting. To the reader,
I'm probably already tired of the empty nonsense
praising "tire" cars. So,
Dear owners of the "old" Spectra-
mov! You have a real opportunity
opportunity to breathe new life into your Penta-
gon (Leningrad, Profi, ATM, ZX-777
etc.) by organizing in your computer
yuter of a real buffered computer
yuter tire, which has become standardin
St. Petersburg, as well as throughout
our country. Away with all the torment and glitches
setting up the configuration! From now on
The inclusion of standard peripherals will be consistent
be born with a pleasant feeling of incoming
into the peripheral card slot! B
next issue, and not in this one (by
why, we will now explain), we will present
We present to your attention a diagram of a universal
bus driver for any Spectrum
room-compatible computer, the above-
no tires. The scheme will be
installed with full technical analysis
operating principle and recommendations for
design. This statement
the swarm worked for us for a year and
showed excellent results. On one
four peripherals worked smoothly on the bus
rial devices in the absolute absence of
Twee any suspicions of glitches. We
absolutely sure that this tire is "pro-
pulls" both five and six peripheral mouths
swarms provided there are no conflicts
by addresses (in our time such devices
no, but if they appear, then their developers
- lamers) and the proper power of the pi-
tania.
Why don’t we specifically publish the diagram?
right now? Don't think, please
please that we “press” the material so that
extend the article into two issues. At first
we wanted to cram everything into one big one
article, but, having thought about it, or rather,
collecting them ina bunch, we realized it was urgent
publication of the scheme will lead to absolutely
the opposite result than we planned
I eat. We are even glad that we stopped in time
foxed
So what did we understand? Here's what.
After the publication of the scheme, inspired and
inspired users with hot
they will rush to mess with their computers
ry with their hundred-watt soldering irons and
fall into the position of Mr. Tailor
(see the beginning of the article), which will lead to
mass burning of innocent people
Spectrumchikov. Therefore, to the eyeballs first
parts of this publication we will give you
so many useful tips:
Tip number zero.
Cool down if they get hot. I'll seriously consider
mother, do you really need a form-
Tire Rotator?
Tip one.
Weigh your strengths and handling skills
with a soldering iron (you have time to practice
practice handling it, practice
on anything but your own
computer!). Get it out of the dusty corner
diagram of your car and, if nothing else
you see, then at least get used to the
how to handle it,train
on anything but your own
computer!). Get it out of the dusty corner
diagram of your car and, if nothing else
you see, then at least get used to the
code and names of signals.
Tip two.
Carefully unsolder all hanging peripherals
riya, if any.
Tip three.
If your car is even a little dim,
reads without periphery - if you please, give
it into condition (no
there should be no trace of glitches).
Last tip.
Wait patiently for the second number "SPECTRUM
EXPERT " - its release is just around the corner!
Share your thoughts about the article