Inferno #10 30 апреля 2007

Железо

DIY - Universal TAPE interface. Scheme of loading and recording tapes.

  The scheme appeared a few years ago, would
la debugged and lain in the fact that
forgot to finish one resistor in the already "over
battered "image ...


   To begin with, that no one competent, pro
marching through me, it was not a normal scheme
download, and write too ... But if UB
Wen recording of "circumcised" automatically, MA
gnitofonom, the ADC load demanded considerable
with respect to development. However, the firm
schemes at the Shelter problems should not be, but I do
somehow have not seen ...

   All of the schemes, pass through me, have been
on K561LN2, which has usually collected
FLASH-generator (since the counter division
human impulses are rarely installed). Y
All schemes have been some shortcomings,
degrade the performance of the tape. Download often
turned into a nightmarish ritual tolerate
that not everyone will agree ... Debug
scheme and effectively used their I
came to the very sad conclusion: if
in the olden days, the same ones when Speccy
We just got let out, they are provided with
were normal circuit load, and quality
in / quantity of our tape recorders have been on
better, the number of Speccy (due to
increased orders) and literacy
- Would have been significantly higher ... But so
decreed the fate of ...

   I was lucky! First the 48th computer, ky
POW me once, was the St. Petersburg VA
invariant of, or Leningrad, as should those
Now judge. Scheme "without surplus and ISSA
chnoe ROM, for some reason a post-Throw
sa black frame and the inscription: ... DIDAKTIK
SKALICA ... Some handy, and possibly father
other (DEAD ANGEL 'a), debug circuit to
LN2, and it was very successful weight.

   However, failures byli.Dazhe on their records
sometimes, but rarely. Had to tighten up
head to achieve a load of other prog
Ramm, almost all of which were games ...

   At first I did not know how to work with flax
one then knew how to make a autorun
their programs (descriptions BASIC was not).
Then he began to make copies of themselves, with "binding"
of head to no one standard - the cascade
Sete with music (such as proprietary). Udi
vlyalsya downloadable from the "chewing" tapes
(After some time when "smoothing
were ") and chromium -" black ", partly
"Crumbling" ... In short, it was a nightmare!

   Clicking on the Pentagon 128, I do not forget to
Shmarov, which I kind of like ... But
dosobrav Pentagon's scheme of its Raspe
Chatcombe, was horrified! Loading was to avert
belorussian! And only some of the programs, with special
strong level gruzilis.Vspomnil and words
Steve / ADG, who warned about this
curiosity, and a little disappointed because
Bad help message better
companies with the old carrier. Then I re
shil correct scheme, echoing sound - with
48-th.

   Imagine my surprise when, and
This scheme began to work somehow ... I
changed the details a couple of times and realized that it
not in the scheme, and in its application. She
nice work on simple models,
but ill-suited to the more complex. Vova
Makarov noticed that simple components of more
correctly wired power supply, and track
ponadezhnee ... The noise level at a joint
rennom computer is much higher, and they
"Break" a weak signal from the tape. High
frequency loading rate violating data
GOVERNMENTAL. To understand this, I wrote a small
aaplet that turns the flow of information from
Ribbon flow durations of zeros and ones
down, and then analyzed the information available through the
STS. Just wanted to get some
games (with quite good - the ear - the level of written
system), but the download process stopped spontaneously in
different places. What I saw in the STS?

   Frankly, I do not remember for a long time
STI intervals, which I received in my
program, but is defined as follows: 7 - Synchro
Organization, 25 - a pilot-tone, 30 - "1", 15 -
"0". The following data should look like examples
Approx so (dropping almost all the pilot tone):

.. 25,25,25,25,25,7,7,15,15,15,15,15,15,15,
15,15,15,15,15,15,15,15,15,15,15,30,30,15,
15,30,30 ..


   In this example, the first is zero
bytes, then bits 0,1,0,1 ...

   And now look at this as a signal
broken Noise:

.. 25,25,2,2,21,25,25,7,1,2,5,15,15,15,15,
15,15,2,3,12,15,2,2,14,15,15,15,15,15,15,
1,1,15,30,30,15,15,30,27,1,3,2,1,26 ...


   As we see, "detail" places "takes" from
normal data of their length. But fear not
this is because reserve the duration of the data model
Jette save them (except for the moments with sinhrosi
drove). Loading will be aborted error
if it is found the interval too is maximal
cue for a standard or large. And if
a large interval may be the completion
writing rather than precipitation data, and not result
children in an error (match the last byte parity
surface), then a small range - uniquely
sign errors, and eventually - failure!

   In this example, large dips
- Fallout - in the stream there. They can
meet on a damaged / mint ribbon
in low / demagnetized signal when no
proper mechanism or tape (it tightened
IU). Small high-frequency loss can also
occur at the weak record (level of noise
mov tape at all noise channel reproducible
product), but almost always they appear
in the computer, in his imperfect ADC!

   Given the strong interference in the computer, from
its digital circuitry, we can assume that the system
chased from the tape already broken melochyu.No level
interference is still very small compared with the self
Mime signal. Therefore, its sine curve, with pre
dominantly large extremes, well
protsifrovyvaetsya in zeros and ones. However!
Sign change is accompanied by the passage of
through 0, when the signal interference is clearly the 
predominant yields. At such moments, a trifle shows cross

BOJ, as reflected in the example. But the procedure
BitTorrent may not recognize the very short
failure, why can not skip the beginning
recording, and then sometimes fail. Why so?
Because the intervals of interference will vary,
and the loading procedure can "catch" more
long, which rarely happens. But the interference
may consist of several bursts, and
if not the first one, and the subsequent
will lead to a breach of downloads. If the Chairman
tavit that the sine wave signal has a value
siderable amplitude, the change in sign of
proceeds very rapidly (rate of change
voltage is high and, therefore, passage
behavior of a 0 - very fast), and interference
barely have time to show themselves. Bursts of noise
will be very short, and loading procedure
they do not perceive. Therefore, the signal with a large
amplitude can be very successful to boot.
But in the end, the latter may polubit
contain a spike noise (after all, the next
bits missing). I am sure that Vlad
traffickers old computer know hurtful
The situation: Georgia - Georgia, as a result -
Reset! Bummer specific and quite explain
myy.Bolshinstvo schemes did not have condensation
torus feedback, which is just pos
will suppress interference. It was enough for him
supply (sometimes units pF) to
Loading become acceptable. By observing the signal
in the debugger, I tucked in Conder. As a result,
reshena.No problem was not at all! I
build a more perfect scheme, with protection
one of intense bursts and selected field
heat component among the noise. Remember,
Dave / ADG told how he exploded
LN2 (already in the ceiling of a piece of chip bounced)
when he gave the signal to the speakers.

   The above diagram is my rule.
Thinking about downloading through the phone, but
through the transition to a transformer, not stress
muyu (not directly advise), I used
high voltage capacitor and a strong hysteresis
Torr at discharge vhode.Dlya Conder inlet
is 1 Mohm. Next stop on the diodes
bound to the ground and the primary rezyukom
suppression - the condenser. Then
limiter / amplifier on one element,
again with Conder, and comparator. That
everything! However, the scheme is not simple.



   And, of course, provides FLASH-generator.
If this generator is not needed, connect locally
the boom of the scheme, and a capacitor and resistor
place, and connect the 13 and 14 feet mikruhi.
Then we can replace the 470 uF 100 uF, and
33 ohms to 100 ohms.

   All the diodes on the circuit - KD521 or equivalent
silicon.

   The scheme written for voltage levels
different cases:

  - The film with the defects, when the record can
be weak (30 mV);

  - To call the phone when the maximum pain
shoy signal (120);

  - Open circuit with an inductance, when
possible surge of high voltage (670
B).

   Frequency:

  - Feed Me: 30 Hz - 17 kHz;

  - 5 connected components: 25 Hz - 20 kHz;

  - 2 connected companies: 8 Hz - 200 kHz.

   Besides, I have decided rasfiltrovat pi
tanie.

   To be fair I should mention that, without financial
ltratsii power everything loaded fine, and not
are elements in some cases not necessarily
positive. But ignore the surplus and no
of the rather big, but the responsibility scheme
just stupid! By the way - the same generator
its weak hindrance reduces the likelihood of
loading in some confusion.
If it is not needed, the scheme can be simplified.
However, the logic should be connected by hanging
first input to positive (for convenience), and filtering
truyuschie elements of the food chain does not exclude
(Although to introduce them to the Pentagon 128 very
inconvenient).

   Scheme Output (DAC) seems unnecessarily
difficult, but not without meaning. Resistor signed
raet output to positive, given its "technology
cally weak. "Further, the actual Delhi
Tel filtered and lineariazatsiey character
characteristics of the output. When done, calculated
shaft on the resistance standard I / you
moves and the amplitude of the order of 0.3 V.

   As a result, we get a very cultured Institute
terfeys which pofigu - from ship
and to write. Not afraid of anything! Shortcomings
ki, of course. Not the best selection
signal from noise (although for such a simple
scheme - normal), not the most powerful output,
Although the "soft", not the best frequency characteristics
acteristic for standard protsedur.Poslednee
explained by the full frequency range
(20-20000 Hz), in which crawls interference
distort the signal (if damaged / unsatisfactory
chnoy record). In some cases succeeded in
gruzhat using an adapter, which
separately cut off the extra frequencies. But this
for a really crappy cases. Stock
also has the advantage, if you combine the carrying
How many computers in a TAPE - local area network. When
This scheme enables you to connect input
and output, and then use only 2 con
Yes: minus supply (GND) and signal. So it is possible
together, probably, the components 8, although only one
of them can be used for transmission on
others - at any time.

   Really do like I do not lokalku
tried it, and therefore listed on the scheme
data - conventional (figured). Limitation
17 kHz for magazines (and then - the fourth type)
explained by the imperfection of broaching tape
and loss of these high-frequency signals (therefore
and they are suitable only for synchronization, not
extended data).

   For the universality of tape loading
should be able to cut the frequency and
desirable "in the process." To trim the HF in
the first logical element can post
vit variable capacitor. And for the LF at
exists to use a set of input capacitances
switching. Change the capacity of more
than 20 times inappropriate.


   This scheme equipped for 4 companies.
Works great! Using a burner player
with microphone input through the special variables
rehodnik / divider (built-in metal
sky shield plug). The trick is the coefficient
coefficients of the division. If you let too much more
lshoy level player, then his scheme, one hundred
rayas pin signal will distort his UB
Wen, and it will no longer boot. Head
Of course, do not touch, even though many of the old
pisi just do not get (better through
some old tape recorder). In practice
deviation and the speed difference for Speccydannyh not 
terrible. In some cases, the effect yields the function 
MEGABASS, which By the way, and the tops of the lifts. But the 
correction type of tape, it seems, only worsen ... Auto

volume limit is not using. Provence
ryayu record on its average level. But for
reliability and at the maximum level should
ship (possible defects may manifest
be).

   Ship better with one hand (I
switch for each). Defects on the tapes
- A rarity, but there are! In general, for all
disadvantage is a very reliable vehicle.
Sometimes to download old records arrive at
ried out under fleece underlay pruzhinku
cassettes. Can rasshatatsya / depart Contact
in the nest (on board) or a plug. Once
After recording one channel was weak.
Case or in a piece of debris on the head, or
a particle of foam springs which fall in the
tape. In both cases - the smallest gap of
barely visible crumbs strongly quenches the record.
Brush my head, basically, before recording or
after the old lent.Dlya download problemati
chnyh tapes perverted in every one. Private
blocks "blockbuster" BAGDAD had
ship, changing the level of individual moments
volume and switching channels on the fly ...
Use a cool, clear copyist,
without strips and counted. Generally, in the presence
presence of 8-bit ATsPa and, of course, with great
memory can be problematic to drive the flow
in a file and digitize "visually and logical
ki ", through their own applets.


                       By KSA-7G 28.4.2007