Keil Ruben:
You are asking a question that indicates that you are trying to run before you learned how to walk. I would suggest that you investigate the well known original Intel publications on the whole 8051 architecture. These are available for download....just click the button to the left and scroll down to the Interesting Sites section and find the Intel MCS-51 Users Guide.

This schematic also shows how to utilize a 74HC138 in a wiring setup to generate set of 8 chip selects for memory chips. You can change this to use one or more of the selects for other types of peripheral devices that have the typical CS/ WR/ and RD/ control signals.




Michael Karas

Note: I posted an earlier version of this schematic in This Posting . There I acknowledged the original source for the graphic, which I modified. Thanks again to PJRC.COM, LLC.