If you are using the external data buss to parse/fetch data from external RAM you won't need pull up resistors on P0. They have strong internal pull ups when used as the external front side bus.Attached is my 8051 development board with 32Kx8 SRAM 61256.
Where do the 3 wires on the SRAM ie. /OE, /WR & /CE go to?
Can I leave the /EA & /PSEN not connected? I know I need to put 10K pullup resistors on port 0. The schematic is done in a rush.
On the RAM -
/OE would go to the P3.7/RD pin on the 8051. This is the read strobe input.
/WE would go to the P3.6/WR pin on the 8051. This is the write strobe input.
/CE is typically used as a paging pin to lock the memory chip into a block of memory. This pin should go to P2.7/A15. This locks the memory chip into the 0x0000-0x7FFF region of memory space. Reads/writes to the 0x0000-0x7FFF will read/write to the memory chip while reads/writes to the 0x8000-0xFFFF region will do nothing unless some other piece of hardware is using that address space.
/EA = External Access. This pin must be tied to +Vcc if using the 8051's internal program memory
/PSEN = Program Store Enable. This is the read strobe when using external program ROM. It does not get used when using internal program memory and can be left disconnected.