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Принципиальная схема CD32 Keyboard to Serial Interface 2- техническая информация, формулы расчета, описание

Навигатор: QRZ.RU > Радиолюбительские справочники > Справочник компьютерного инженера

CD32 Keyboard to Serial Interface 2

Date: Thu, 20 Oct 1994 11:07:00 +0100
From: 
 (Klaus Hegemann)
Subject: Re: Using Auxiliary Port as Serial Port
Message-ID: <
>
References: <
>
Newsgroups: comp.sys.amiga.cd32
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Hi Stan !
 s> I understand that you can use the auxiliary port (keyboard) as an
 s> RS-232 port and that this is what sernet does.  But when I look at
 s> the pinout, there is only clock and data signals, not ser-in and
 s> ser_out.  What am I missing here?
Well, I think you refer to the A4000's kb.jack pinout. It's 'almost'
the same as you can find at the cd32. But the difference is, tataa..:
on the cd32 there are additional serial-interface-signals connected
to the AUX-jack. You can find them at the former unused pins.
The mess is, that the (serial-) signals carry [negated] TTL-level.
As a result, you have to make sure that there is a level-conversion
before you connect them to other computers. Without you surely kill
your cd32.
The cd32-FAQ shows a rather complex (but quite correct) way to do this.
(Aehm, the level-conv., of course ;-)
If you plan to connect the CD32 with other Amigas then I found out a
rather easyer/cheaper way to solve that:
Amiga                    |\ |                         Amiga CD32
             TxD o-------| >|---.
level: RS232             |/ |   |                     level: /TTL
-12V..+12V            D1        |                     0V..+5V
                               .-.
                               | |
                               | |        IC1
                             R1| |   ''''''''
                               `-'   '  _   '
                                |    ' | \  '
                                *------|  O-------->o /RxD Pin6
                                |    ' |_/  '
                               .-.   '      '
                               | |   '      '
                               | |   '      '
                             R2| |   '      '
                               `-'   '      '
                                |    '      '
                                |    '      '
                                |    '      '
                               ===   '      '
                               ///   '   _  '
                                     '  / | '
              RxD o<-------------------O  |---------o /TxD Pin2
                                     '  \_| '
                                     '      '
                                     ''''''''

              GND o-----------------------*---------o GND
                                          |
                                     '''''|''
                                     ' o  o '
                                     ' |7 14'
                                     ''|''''' IC1
                                       |
              +5V o--------------------'
the pros. and cons.  ([1]this solution ./. [2]max232-sol. (->FAQ) )

pros.[1]:  easy to solder
           cheap
           fits within a SUB-D 25 plug
           does not consume CD32 +5V power ;-)

cons: 'dirty' solution; i.e. circuitry makes use of the 1488/89 tolerances
      you may only connect Amiga-computers to your cd32 when using THIS
      [1] circuitry - since they all use the 1488/89 chip set.
      PCs 'may' work, too. But interface board must contain 1488/89 chip
      set.
      I do believe that this will work on all Amigas -I tested it at least
      on 3 different Amiga-models, however, there is still no guarantee
      that this will work on yours.

However, I use both interface-types since about 6 months.  There has
been no problem yet.

 s> Also, has anyone made their own connector to the expansion port to
 s> pull off the RGB signals?  I'd appreciate hearing of your experience.

Yea, does work fine.  In use for about 6 months; and still no probs, too.
For details refer to the cd32-faq.

I am not quite sure about the cd32-pin numbers, just take a look in the
faq.

bis den bald
Klaus

[---------------------------------------------------------------------------]
Date: Fri, 21 Oct 1994 14:55:00 +0100
From: 

Email  (Klaus Hegemann)
Subject: Re: [2]Using Auxiliary Port as Serial Port
Message-ID: <Email >
References: <Email >
Newsgroups: comp.sys.amiga.cd32
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Hi!

'updated info:'
       Amiga 500,2000,1200,...

       level: RS232
       -12V..+12V

                          |\ |                         Amiga CD32
              TxD o-------| >|---.
              Pin2        |/ |   |                     level: /TTL
                       D1        |                     0V..+5V
                       1N4001   .-.
                                | |
                                | |        IC1 7400
                             R1 | |   ........
                            (*) `-'  1:  _   :
                                 |   ___| \  :3
                                 *--*___|  O-------->o /RxD Pin6
                                 |    : |_/  :
                                .-.  2:      :
                                | |   :      :
                                | |   :      :
                             R2 | |   :      :
                            (*) `-'   :      :
                                 |    :      :
                                 |    :      :
                                 |    :      :
                                ===   :      :
                            GND ///   :   _  :4
                                     6:  / |____
               RxD o<-------------------O  |____*----o /TxD Pin2
               Pin3                   :  \_|
                                      :      :5
                                      :.......

               GND o---------------*-----------------o GND Pin3
               Pin7                |
                                   |  ........
                                   | 7:      :IC1
                                   *--:GND   :
                                   | 9:      :
                                   *--: \    :
                                   |10: |not :
                                   *--: |used:
                                   |12: |    :
                                   *--: |    :
                                   |13: |    :14
                                   `--: / +5V:-.
                                      :......: |
                                               |
                                               |
               +5V o---------------------------'
               Pin4

            shield o=======================! [n.c.] o shield
               Pin1

The RS232-TxD-signal carries +12V or -12V level. As the first step
in conversion the diode D1 blocks if the signal drops to -12V.
In this case the voltage divider (R1,R2) is only connected with
GND potential. So the gate input carries GND level, too.
When the RS232-TxD-signal changes to +12V the diode will pass it
through and the voltage divider now provides a +5V-level signal to
the gate input.
The backward conversion consists of simple negation of the cd32's
/TxD signal. In fact there is no level conversion.
While the conversion for the received signal does
work proper with any RS232 opponent, the sended
signal furthermore carries TTL-level.
The opponent hardware tries to regain the TTL-level signal from
its 'RS232' input. The conversion unit handles the provided
pseudo RS232-type signals correct (as we want ist to be:-).
(*) voltage divider R1-R2:

   U                      U      = 12V    U   = 5V
    R1+R2     R1+R2        R1+R2           R2
   ------  =  -----
   U            R2
    R2

                               U
                                R1+R2
   I      = 5 mA  ==> R1+R2 = ------   = 2400 Ohm
    R1+R2                      I
                                R1+R2

                     (R1+R2) * U
                                R2
   U   = 5V ==> R2 = -------------  = 1000 Ohm; R1= 1400 Ohm
    R2                  U
                         R1+R2

R1=1500 Ohm
R2=1000 Ohm ==> I=4.8 mA ==> U(R2)=4.8 V   ..  will be OK

IC1 = 74LS00  (4 NAND gates)
D1 = e.g. 1N4001
have fun !
be careful; I am in no way responsible for any damage that may result.
CU
bis den bald
Klaus                    
Contributor: Joakim Цgren
Source: CD32 keyboard port info usenet posting by Klaus Hegemann

Информация предоставлена справочником The Hardware Book Team 1996-2004.

Навигатор: QRZ.RU > Радиолюбительские справочники > Справочник компьютерного инженера

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