8051 standard memory connection?

[PCBwire]

Want to use external ram and rom for 8051 and program in keil C.

I am not sure how keil C need 8051 to be connected to ram and rom.


As i understand till now:

1. output from P0 lines AD0 -AD7 and latch it with ALE/P\.
2. output from P2 lines AD15-AD8, from latch AD0-AD7, and input 8-bit data on P0.
3. for rom use psen as output enable.
4. for ram and devices on ram address space use rd, and wr.


Not sure for:
1. Is there way for P0 on first output AD0-AD7 cycle, that there will be input data , and if so should direcion switch be used?

 

[IanP]

When you connect external ROM and RAM to 8051 you have to latch the lower half of the address bus and that is done, for example, by the 74LS373 controlled by the ALE signal .. eg. see attached picture ..
Also, EA pin has to be grounded ..

With all the above in place - the hardware is ready, software (Kiel or whatever else) that you use to compile the hex file doesn't matter ..

Rgds,
IanP

 

[PCBwire]

It works thanks.