Function bank_port_kernel 

pub fn bank_port_kernel(
    write_valid: bool,
    write_address: b16,
    value: [b8; 18],
    read_address: b16,
) -> In<[b8; 18], 16>

One cache bank’s port: write position p of a chain, read the signer’s address.

• write_valid, write_address, value: the factory’s write of one 18-byte node (the same address for all four banks, a different value).
• read_address: the signer’s read row (the same for all four banks).
• Returns the bank’s RAM input. Combinational; no registers.