Schematic for Dummy Cartridge
This modification tricks the computer into thinking a cartridge is
installed. This is a terribly crude attempt at a schematic for it,
since the original notes I had are quite old, and were just a few
scribbles. I'm sorry that I don't have better references to the
pins of the Atari board for the cartridge port, but I'm sure you
can figure them out.
Parenthesis in the diagram indicate that the two lines are not
connected.
Switch
+--/ -+
| |
+---------------------------------+ +----+
| |
| | | | | | | |
+----------------------+ |
+ 14 13 12 11 10 9 8 + |
+ + |
+> 7404 Hex Inverter + |
+ + |
+ 1 2 3 4 5 6 7 + |
+----------------------+ |
| | | | | | | |
+----+ | | |
| +-----+ +-----------------------+ |
| | | |
| | Pins on bottom of circuit board for the | |
| | LEFT cartridge | |
| | +--------)--+
| +-----------------------------------(--+ |
| | | | |
| | O O O O O O O O O O O O O O |
| | |
| | O O O O O O O O O O O O O O |
| | | | | |
| +--+ +--------------------------------)-----+
+----------------------------------------+
Pin 14 of the 7404 connects to one side of the switch
Pin 2 of the 7404 connects to two of the cartdige port pins, all
other pins of the 7404 connect to only one.
Atari 800 Computer upside down, keyboard toward you
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:
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 ;-)