Apple II Bus Access

All Apple II bus signals can be picked up directly from the VIAs next to the edge connector.

A few signals, R/W, STROBE and I/O SEL have special VIAs located on the board, where you can pick them up.

Power (+5 Volts) and Ground can be picked on from the VIAs located near the 74LS245.

If you don't need or wish to use the 6522A VIA, you can pick up most, if not all of the Apple II bus signals that you might need from the pads used to connect the 6522A VIA pins 21 through 38, which are labeled with their function. Here is more detailed explanation of what these signals are.

IRQ	6502 interrupt request - low true signal connected directly to the Apple II peripheral connector. Should be extendable to a remote bread board, if you keep extension cable short
R/W	6502 R/W signal - this signal is buffered by the 22V10 GAL, to allow for additional fan out or usage of a remotely located bread board
SEL	Apple II Device Select signal is connected directly to the Apple II peripheral connector - Asserted by the Apple II when address c08X plus 10 times slot number is accessed. Since there is not any fan out on the Apple II motherboard, you should be able to extend to a bread board, if you are careful and keep extension wiring short
CLK	This clock is a delayed and shortened O2 clock needed for interfacing with 6522. I call it a synthesized 6502 O1 clock, though it extends longer than a true O1 clock would extend. Since it is generated on the SUPERPROTO card, if you are careful, you should be able to extend it to a bread board
D0-D7	This is the peripheral card data bus, which is a buffered version of the 6502 data bus. You can read valid data from this bus when SEL is asserted and R/W indicates a write cycle. You should only write data to this bus when SEL is asserted and R/W indicates read. Since it is buffered, you should be able to extend it to a bread board, as long you take precautions to keep extension cable short and minimize fan out
RST	Apple II System Reset - low true signal indicated systems reset. Connected directly to the Apple II peripheral connector. Should be extendable to a remote bread board, if you keep extension cable short and minimize fan out
A0-A3	Low four bits of Apple II address bus. This is directly connected to the Apple II address bus, so be cautious about extending.