HI, i am working on a project. I need to give extrnal data to input of buffer 74ls373 and at the output pin i receive data on pins D0-D7 which is given to the input to the microcontroller data pins (P0). I am using external memory for RAM and ROM.
My problem is when and how should I read data output pins of the buffer and store the output result into external RAM.
That all depends on how much memory you have, and on a lot of details of your hardware: the particular 8051 variant in use, your memory decoding logic and other things. This is a hardware issue. Keil tools have nothing to do with it, so you're off-topic here.