rfc@briar.philips.com (Robert Casey;6282;3.57;$0201) (09/05/89)
BASIC CART MODIFICATION
Installing a switch on the cart so Basic can be
switched on or off without removing the cart
I own an Atari 800 and about half the time use the Basic cartridge.
Other times I use programs that require that the Basic cartridge be
removed. This can cause a lot of wear and tear on the 800's
cartridge slot. To avoid this, the cart can be modified so it can be
switched in or out. I took apart my Basic cart, removing the shell.
I cut the circuit board trace connecting pins 13 and 14 on the
cartridge board (pin 14 is the source of memory map control signal
RD5). I installed a very small (approx. half inch long, and
quarter inch tall from the bottom of the switch body to top of
slider) slide switch (SPDT) on the top edge of the board, center
contact soldered to the +5V trace (the fat trace at the top IC side
of the board). The other contact is connected to pin 14. This
connection is made as far from the bottom edge of the board as
possible so it can be pluged into the 800's cart slot without
jamming. The metal housing of the switch should be connected to the
+5V trace to form a static drain (be sure it doesn't short to the
access door's metal shield; the metal shield could be removed if
necessary). The cart board is inserted with the chips facing to
the back of the 800.
When I want to use Basic, I open
the access door and set the switch to "B". When I need to remove
Basic, I turn the switch to "M", for machine code programs. This
causes the circuits in the Atari 800 to switch away from the cart
and to the RAM at the same addresses. The cart is effectively
removed. I rarely use other carts, but if I want to, I can still
unplug the modified Basic cart.
switch mounts on the top edge of the board
_________________
I +5 trace I
I ---- ---- I
I IicI IicI I
I I I I I I
I I__I I__I I
I I
I I
edge card conn.
+5V-pin 13^ ^pin 14-RD5
plug board into computer so that the ic's face
the back of the computer