http://www.8051projects.net/ Learn to make simple microcontroller projects, pic, 8051, avr and arm projects. download 8051 projects, tutorials, libraries, sample codes. join the microcontroller discussion forum and ask doubts regarding electronics. the best source for 8051 over internet. en-gb 2008-12-01T22:57:23-08:00 contact@nospam.com hourly 1 2000-01-01T12:00+00:00 http://www.8051projects.net/forum-t10364.html 2008-12-01T22:57:23-08:00 i m given a task to use AT89C51ED2 which is one member of 8051 family . if i using it to interface a LCD via port 2 , do i nid to put pull up resistor ? whats the main purpose of putting pull up resistor ? are this apply to port 0 as well ?Thank you http://www.8051projects.net/forum-t10364.html 2008-12-01T22:57:23-08:00 ntung P2 does not requires external pull up resistor as P2 already has internal pull up resistor. Only P0 requires external pull up resister when interfacing with external devices because it does not have internal pull up.