Question about the pin wiring

[JumpLink]

Sorry, I have absolutely no idea about electrical engineering but am trying to understand it right now, so I have a few questions.

Why is it not enough to connect pin 22 to RDY0, why do PA1, PA2, PA5 have to be connected to it as well?

If I read the documentation these pins can be used for the following:

• PA1: is a bidirectional I/O port pin
• PA2: is a bidirectional I/O port pin
• PA5: is a bidirectional I/O port pin
• RDY0: is a GPIF input signal

Or:

• PA1/INT1: is the active-LOW 8051 INT1 interrupt input signal
• PA2/SLOE: is an input-only output enable with programmable polarity for the slave FIFOs connected to FD[7..0] or FD[15..0]
• PA5/FIFOADR1: is an input-only address select for the slave FIFOs connected to FD[7..0] or FD[15..0]
• RDY0/SLRD: is the input-only read strobe with programmable polarity for the slave FIFOs connected to FD[7..0] or FD[15..0].

What are they used for in the PiPU?

I think the RDY0 (as SLRD) and RDY1 (as SLWR) is used to recognize when the NES reads and when it writes to the memory, right?

Why is PA4 wired to Ground? In the documentation it is used for

• PA4: is a bidirectional I/O port pin.
• or as FIFOADR0: is an input-only address select for the slave FIFOs connected to FD[7..0] or FD[15..0].

[rasteri]

As far as I can remember :

RDY0 is used as SLRD, it automatically clocks the data out of a FIFO into the data lines.
But we can't read SLRD in software so we have to route it to GPIO (PA1) as well, this is used to detect VBLANK
SLOE enables the output of the chip, this is how ROMs operate so we need to do it too
RA5 flips between the read and write buffer, I can't remember how this works exactly

[JumpLink]

Thank you very much for answer @rasteri, I think this will help me

[Workraft]

Thank you very much for answer @rasteri, I think this will help me

@JumpLink
Did you manage to finish it?