how to use 74ls595 in avr for seven segment drive .

hi ,
I am working rtc by avr with seven segment .
but which is the best way to drive seven segment by 74ls595 useing avr .

If you know how to drive 7-seg using an 8-bit port then its easy for you to drive it using 74ls595 shift register. The only difference is you need to serial out that 8-bit data to shift register instead of moving it directly to port. after data is shifted out completely enable the latch. Best thing about using shift register with latch is that if you use shift registers in a chain mechanism (each 7-seg has its own shift register connected) then you dont have to refresh your display again and again. Once displayed its done your controller is free to do other stuff.