Laboratory - On connecting external devices to the ZX-Spectrum.
LABORATORY
About Connecting external devices to
ZX SPECTRUM
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(C) SSSR
Here I want to tell you about, what
I ran into problems by connecting external
device to the ZX. Somehow came to me
KVAZAR and asked to pull up the modem to CDOS
his "COMPACT'u. It would seem simple:
looking at the board companies signals corresponding to the
same on the modem and unsolder one to one. So I did. Turn on
comp and waits for me the big bummer. EMS, as did not see the
modem, and can not see, though of BASIC can be controlled. It
turns out that it that every device I / O
in the computer, when activated signal IORQ,
considers it his duty to stick on the data bus every gag.
Priority here depends on the particular circuit implementation.
In "COMPACT'e" queried Kempston - joystick in the company
"SKORPe" in 1994 - the port FF, even in some comp get underfoot
AY. Only two companies among those that fell into my hands for
the improvements, behave decently. Somehow, one of them was my
signature "SCORPION", 1992, vypuschnny one of the first.
The point here is this: if you select some external device,
it should block all the others that they do not interfere with
each other. This problem can be solved in two ways.
First - use the full (hard)
decoding. However, not always convenient
model for same-modem dozen other diodes or several buildings
shallow logic moreover, as yet to a wide loop, overloading the
address bus. Therefore preferred the second option - to lock
the I / O signal IORQGE. To do this, you must enter it in the
complex (where it's not). Here again there are two options.
The first - to pick off 20-foot processor
from all other compounds, and solder in a gap resistance of
430-820 ohms (selected experimentally before disappearing
Gluck), as done in the "SCORPION'e" and "KAY".
But it's better to do it differently, though for
This will require an element 2ILI (LL1).
If the board is free - it can be
use, otherwise the solder will have a chip K555LL1 second floor.
D1-K555LL1
IORQ> 'to the rest
> Scheme
IORQGE>
/
2.2 to
If an external device active
is low, such as 6-I
KR580VV55 foot in the scheme of the external port or
4-th leg K561LN1 in the scheme CDOS-modem, then
need to select the signal from input proinvertirovat and apply
for IORQGE. This is easiest done by placing an inverter on the
transistor KT315. If the external device is the active high
level, the signal choice immediately throw at IORQGE.
By ___ +5 B
__ 1k /
CS ____ B | / KT315 (n-p-n)
> ____ | <-----------
| \
470 / E \ ______________
IORQGE
Strange that this does not say citizens of Minsk, which I
ring up after the first unsuccessful attempts to pull up the
modem, for hard to imagine that among the tens of
computers to which they connect the modem, did not find those
in which there would be no such problems. Well, okay, Whatever
it was, I'll be glad if anyone, this information can help you.
And yet, like, say a few words to the now-defunct St.
Petersburg firm CREATE SOFT and LOGROS.
One of these days I connected a controller
kempston-mouse to COMPACT'u. According to the original
instructions wired system connector and redid the mouse, as
described ZX-FORMAT-5. Turn on the computer and run the test.
Observed such a pattern: regardless of the direction
movement of the mouse, the cursor moves only in
one side (or right or up), the only joy that the buttons are
pressed. And when off the mouse cursor twitches,
as obdolbivshiysya. Again began to think what
here it. Scheme on the controller is not well
although chips are not erased. Considering
diagram of the controller in the newspaper OPTRON-13, drew
attention to two trigger K561TM2, standing at the entrance. The
product is from CREATSOFTa none found. Outputs with the mouse
primed directly to the inputs of the counters and because of
their high sensitivity, the controller responds to false
positives and can not correctly determine the direction of
account. Therefore it is necessary to burn on
Controller second floor TM1 or TM2, and
also underpin inputs Xa, Xb, Ya, Yb resistances of 10 ohms to
+5 V to When disabled the mouse cursor is not twitching.
In addition, the controller or in the instruction
were mixed on connection between a
two signals ...
It is interesting to put yourself in the ordinary user,
usually poorly versed in the gland. He goes to the firm buys
controller for a decent price of about $ 10 and receive
assurances that everything is in order, works great, you only
need to connect properly and rulis myshoy health. He connects
the controller and watch about the same now as it was I did.
Naturally, he goes to the company, changing the controller,
once, twice as long as it does not bother firmacham and they
would say that either it connects properly, or comp buggy, or
mouse is not in order, if at all, nothing say or even sderut
five bucks for a supposedly finalizing company or for the
connection ...
These are the reflections. Those interested in
details on connecting various external devices to the Speccy,
please call me at phone in Gomel: (0232) 50-31-61, ask Sasha or
write to Editorial newspaper.
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Laboratory - On connecting external devices to the ZX-Spectrum.
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