Hi i am using port pin P3.7 (which is " /rd " in chip 89C51RD2)to trigger a 555 timer but this pin is going low even when i am writing '1' to it,thus triggering 555 timer,even when i am not writing '0' to this pin. i am not using any external ram or rom. so " /rd "pin is used by me to trigger 555 but things are going wrong. what should i do to avoid unneccesary going low of P3.7 ? i have to initialise port 3 ? how with keil (so that i can use it for above application) ? Thanks
Have you looked if the level of the EA pin is correct? See datasheets. If it isn't, the device will try to access external rom data and will modify the level of the pin as needed. As such, you will not be able to manipulate that pin yourself. Rgds, Geert