RUSH #01 29 мая 1999

Железо

Development Spectrum - Lock the keyboard port when connecting SPECCY C-DOS modem.

    LOCK keyboard port SPECCY

       When connecting CDOS-MODEM


   Write this article I have decided after
how for months to no avail
tried to connect to your computer
"Compact-128" Ming CDOS-modem. Now
Yet this problem is successfully solved by
an unpretentious device which invented our Homel hard'er SSSR,
for which I am immensely grateful to him.

   Actually, I am a person very far from
iron, so when I ran into similar glitches, I had to resort to
by an electronics professional.

   One problem is that on my "compact", which is widely 
distributed in Gomel, as well as on some other computers, due 
to not fully thought out circuitry there is a conflict between 
the port of the keyboard and an external device such as a 
modem. All ports are either busy or they hang the keyboard. In

An external device can not be
select programmatically, for example,
terminalka EMS just hangs instead of giving the port number 
"--". 


   Let us approach this issue from the perspective of
zhelezyachnika. At first glance, nothing here
No complicated: to connect the modem, as well as
and other external device is quite simple: look for free ports, 
according to the concept of routing bus company Dunn & Solder 
findings according to the signals scheme to the system 
connector, or directly on the processor. 

   Just in case, bring raspayku findings modem developed ARS'om.
 The first conclusion is marked on the board, "1".


      01 - D7 (Data Bus);

      02 - +5 V (power);

      03 - D6 (data bus);

      04 - D4 (data bus);

      05 - D5 (data bus);

      06 - GND (housing);

      2007 - WR (write);

      08 - RD (read);

      2009 - IORQ (IO);

      1910 - A4 (if the port # EF);


   In total there are few standard
ports for connecting CDOS-modem:
 # EF (239) - the most widely used.
 # F3 (243) - for "byte";
 # 77 (119) - for "GRM";
Find a free port is very easy. Enough of any type the following 
BASIC combination: PRINT IN N; where the N-port

in the decimal system. If, after
all this pain and you will see on the screen
255 - that seems to be all right -
port is available. However, do not hurry to be happy we must 
also check the port on the record. This You can do the feeding 
team: OUT N, M, - where N-decimal port number, and M-any

number (0,1,255, etc.). If, in addition to
computer there is nothing strange: the type of discoloration of 
the curb, squeak in dynamics, etc., can congratulate yourself -

port is really free and can be safely
hang on him the modem. Otherwise,
This port is addressed as # FE and want to
or to seek other free ports, or,
if none is found - to tighten
decoding ports (two bits):



    A 0 <1 '
 A1 <2

    A2 <3
 A3 <4 to 9-foot chip th

    A5 <5 80> 555LL1 (DD1.3)
 A6 <6 modem.

    A7 <* 11

            12 555LA2



   However, in my "compact" is not a panacea, because then 
begins to "puff brains "kempston joystick, and the data bus

clogged, which leads to various bugs and
Trouble.

   Of course, this can be cut off kempston
completely, as it did from the KVA
Grodno, in its "CD-128", and put
tumbler. We called the KVA and asked to help with the scheme of 
improvements and new driver for EMS. Victor promised to send 
shemku by regular mail and by Fido, however, two

months we have not received anything from him, in spite of our 
constant calls and requests. So we had to use the old,

well-proven method of educated bet.

   And this button is done as follows:


             D24 (K555KP11) D25


     > KB0 02> KB4 2

     > KB1 05> KB5 5

     > KB2 November 2004 D0> IN November 2004

     > KB3 July 14 D1> KB7 July 14

     > DV0 March 2009 D2> DV4 March 2009

     > DV1 June 1912 June 1912 D3

     > DV2 10 * 10

     > DV3 13 13

   > X 01> x 1
A0 1915 A0 1915

   -IORD0-IORD0



   We are looking at the board, "Compact two chips
D24 and D25 (K555KP11). Cutting the Track
leading to the first two legs of the chips from
Contact A0 and throw released the first leg to the body. The 
result - Kempston no more, no test program

Now you will not find it. Immediately begin to work normally 
"ZX-ELEMENT-1" where before the cursor was constantly activated 
and some other programs.


   Tumbler set to cut the chain: from A0 to
findings "01" chips. You can do this
use any two-position switch, such as "mikrikah.


   But you must agree, this is somewhat
inconvenient - to hang an extra switch,
and then automatically shut off when kempston
work with EMS, MMD, CDOS and the like.

   And here, in the head SSSR comes a brilliant idea - to put 
an ordinary inverter transistor, a blocking read the keyboard 
port (# FE), in order to prevent selection of ports, when 
queried by a modem. 

   Collect elementary shemku:


                      By __ +5 B

                       /

         ____ B | / KT315 (n-p-n)

    <_ \ \ _ | <-----------
          1K | \ E
to the modem: takes \ _____ to 15 feet
value "1" if it is both chips
selected. D24, D25 on the signal
                           signal - IRD0.



   If an external device, through the transistor keyboard port 
is blocked and no longer prevents the poll the same modem.

Feel free to hang up the modem to the port (# EF) and work on 
health in the EMS, MMD and CDOS. 

   Now there is no need to install the switch - blocking is 
automatic and completely transparent for the user. No side 
effects this transformation in the "Compact" does not call. 

   On computers with the correct choice
ports, for example, in the company, "Scorpio"
This revision is necessary.


   Thank you very much hard'ery SSSR for the great idea and 
help in connecting my modem.