Hi Rao,

i want to interface keyboard,lcd,dac and adc to 8051. ..........

Its like you wanno gang rape poor 8051.

3x4 Key borad, you need 7 ports

LCD say, Hitachi HD44780 20*2 in 4bit mode you need 06 ports

there are 32 ports in 8052, you got still 19 ports left out which you can allocate 10 to ADC and DAC thru 1 of 2 type MUX.

Yet you got 9 ports left to control MUX and even use for PWM, interface RTC and a watch dog.....

Hang that on the Miseltoe and Have a lot of fun if you finish that up before Xmas.

Simon