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Article #43 (75 is last):
From: vparada@inf.utfsm.cl (Victor Parada G.)
Newsgroups: freenet.sci.comp.atari.prog.8bit.resource
Subject: Re: Dummy Cartridge for Atari 800 [Correction]
Posted-By: xx004 (aa853 - Craig Lisowski)
Edited-By: xx004 (aa853 - Craig Lisowski)
Date: Sun Sep 18 03:32:30 1994

Hola mundo.

Me  wrote:
>Chad N.R. Knudson  wrote:
>>Schematic for Dummy Cartridge
>>This modification tricks the computer into thinking a cartridge is
>>installed.  [...]
>
>The following does the same for a dummy 16K cartridge.  A friend of
>mine gave me this home made cart.  Since I'm not an IEEE member,
>I just can describe it: [...old description deleted...]

I was wrong about the pinouts. Now, the pinout for the chip is ok
(it is looked from the upper side):

R/W    RD4     +5V         TI  441CP       GND      RD5
 R     14      13          SN74LS04N        B        A
 |      |       |          _________        |        | 
 |      |       |         |         |       |        |
 |      |       +----+   -|8       7|-------+        |
 |      |       |    |   -|9       6|-      |        |
 |      |       |    |   -|10      5|-      |        |
 |      |   250 A    |   -|11      4|-      |        |
 |      |   ohm H    |   -|12      3|-      |        |
 |      |   (?) V    |   -|13      2|----+  |        |
 |      |       |    +----|14      1|--+ |  |        |
 |      |       |         |____A____|  | |  |        |
 +------)-------)----------------------+ |  |        |
        |       |                        |  |        |
        +-------)-----------------o/o----+  |        |
        |       | +---------------o/o-------+        |
        |       |_|          double-switch           |
        |        U  LED                              |
        +--------------------------------------------+

Codes for the resistor:  orange/orange/(purple-brown)/gold  (250 ohm?)

Looking at the cartridge slot from the back (i.e. the space-bar is on
the top), the pins are as follows:

 A  B  C  D  E  F  H  J  K  L  M  N  P  R  S
 1  2  3  4  5  6  7  8  9 10 11 12 13 14 15

Pin R   R/W   Processor Read/Write
    14  RD4   ROM present ($8000-$9FFF ?)
    13  +5V   DC power supply
    B   GND   Ground
    A   RD5   ROM present ($A000-$BFFF ?)

David Davies  wrote:
>What's the point of having a dummy cartridge? Is it useful for anything?

I used it to load an image of Atari Assembler/Editor, assemble and
return to BASIC to test the routine, without rebooting...
You can press the RESET key without loosing the code of the cartridge
usualy wiped out by the screen memory.

... and sometimes to play some games copied from cartridges ;-)

Bye...   ++V
-- 
:           | / . -/-         vparada@inf.utfsm.cl         Victor Parada G.
:   -/- -/- |/ /  / () ( ()   vparada@loa.disca.utfsm.cl  Informatica UTFSM


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