Transcript CBUS_I_Diagrams

COMMODORE 64
CARTRIDGE BACK-UP SYSTEM
(CBUS)
Traces on top side of board that pass under other components.
Top side of board with backlighting to show bottom-side traces.
DIP Switch
Jumper
RESET
Bottom side of board with topside components highlighted in yellow lines.
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Some notes regarding the layout: Some things are not visible from my pictures.
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1. The resistors are yellow, violet, red, gold (4700 Ohms +/- 5%)
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2. There is a jumper wire just above the DIP switches. It connects two traces on the bottom of the board. If you
look at the back, you will see the pads for the DIP switches. The jumper connectors are the two at the very top
connected to the 1st and 8th pins.
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3. The thin traces -- connected to trace # 8, 9, and 11 as viewing the board from the top with the connector
edge at the bottom -- run UNDER the cartridge connector. It's misleading where they come out. The first thin
trace goes to the left under the cart connector and ends at a pad that connects to the underside of the board.
The second thin trace extends more or less straight through to another pad that connects to the underside of
the board. The third thin trace extends more or less straight through to the third pad that connects to the
underside of the board. If you look at the three globs of solder just below the DIP switches, these are the pads
I'm talking about. You will notice two traces between these pads. The one on the left connects to the 8th pin of
the cart connector (counting from the left). The trace on the right connects to pin 9 on the cart connector. The
the right of the pads is one more trace (connected to the resistor at one end). This trace is connected to pin 11
of the cart connector. An easy way to tell which ones are connected is to look at the cart connectors -- the ones
that appear not to be connected are actually connected to the upper traces. These are also the cart pins that
are adjacent to the thin traces.
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4. There are two traces that run under the DIP switches. The one on the left comes from under R1 (leftmost
resistor) and is also connected to the bottom of R1. It connects also to the screw that holds the cart connector
in (ground?). I can't tell where it goes after it runs under the DIP switches. The other trace is connected to R2
(rightmost resistor), but I can't tell where it goes. Both may go to the 1st and last pins of the DIP switch, but I'm
not for sure.
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5. The RESET swtich (lower left corner on the top) is connected to the BOTTOM of the board. It is not
connected to any of the top traces though it appears so. You can see its connection on the bottom of the board.
I included one picture that is backlit so that you can see both sides at once. The PDF file is a quick scan. I'll
clean it up (probably will retype it) and resend it. I included it just so you can get an idea of how the CBUS
worked. You'll see reference to CBUS II in the instructions. I don't have it, but I do have some magazine
(Compute!) advertisements that show it.