Munaza,

Richard is talking about how to make things working as fast as possible. Don't get confused by that at the first place. Most probably you can forget about it, if you don't need extra speed. Your application is traffic lights. If you don't need to change the lights and check the inputs faster than in a few tens of milliseconds (which I doubt), it is enough to connect the data_in-data_out-clock-latch lines of '595/'597 to any pins of 8051 and write the program so that it directly manipulates them (see for inspiration the code snippet in my post above). Read the '595/'597 datasheet for the proper sequence of signals.

Jan Waclawek



PS. Please stop using SMS-like abbreviations (like "u" instead of "you") on this forum.