Hi there! I am building an AT89C51 programmer. I want to use parallel port for the purpose. I wanted to know about the configuration of P0 (data port for programming and veriification). If I write a byte and then read it back, obviously the port will be configured as input at one time and as output at the other time. At what point in time does it switch its state? Is it due to the application of the control word that says "read" or "write"?? It requires address,data,control,ALE pulse,EA (12V). the data sheet follows the following sequence. Only one bit of control (dunno why it didnot mention other bits, may be it is assumking going from read to write), EA (12V),address,data,ALE pulse. Please help.

Regards
Aman