it is said that port 2 of 8051 has internal pull up in both functions (i.e when used as i/o or higher order address). but according to the figure given in manual, it is not possible for port 2 to have internal pull ups in both functions.
the control should be zero either during i/o or address operation. please help ... some websites show port 2 without that AND gate. which is correct?
also my question is, Should we use external pull up when using port 2 for higher order address ?
no need of AND gate for port 2 its only needed in port 0 u can compare below two images you can see that for port 0 you must have use external pull ups
in port 2 case no need that so they don't have AND gate
yes thank you... but what makes me to be still in confusion is that it is the lNTEL's manual that shows the presence of AND gate in port 2. Can u please clarify?
intel manuals have and gate because when you are using port 2 for addressing external ram you have to use it with port 0 so for that you addressing 16bit address for say 64k of ram then higher 8bit address is provided by port 2 so you need only addressing mode then you cant use port 2 as normal i/o port so AND gate is for mode selection.