Re: I/O
It depends.
Recently, I used a chip with only 7 external registers.
I mapped these registers to 0xxxh, 1xxxh, 2xxxh, ~ 6xxxh.
That is I used XBYTE[0x0000], XBYTE[0x1000],... to have access
to this chip. So I did not put 373 on the board. However, not all
applications could use this scheme. Also remember to connect /WR and /RD to your chip for write and read.
8051 <--> my chip
===============
A8 <--> A0
A9 <--> A1
A10 <--> A2
D[7..0] <--> D[7..0]
/WR <--> /WR
/RD <--> /RD
Maybe you need a 373 to latch A0~A7 (8051 shares these pins for
data and address).