Here is excerpted from doc in core 8051 project:
... ...
interface to external program rom:
ea input 1 external access
rom_addr output 16 rom address
op1 input 8 operation 1 input
op2 input 8 operation 2 input
op3 input 8 operation 3 input
... ...
And,i don't really understand what exactly usage of op1,op2,op3,and how can i connect these pins to my off-chip ROM as my external program rom.
Thank u~