interface problems

[mikeb]

im trying to interface a microcontroller port, setup as a input port(high impedance inputs) to a voice recognition module, whos data output pins toggle high then go low, when the board is first powered up or reset.im running the boards from 2 different power supplys,and im wondering what if any, interface i need between the data outputs an controller inputs.also the voice module has 4 control pins which are active low but either float high or are internally pulled high on powerup and reset.i want to control these pins with 4 of the controllers output bits. all 4 output bits are low when the board is first turned on and the active state of the voice module pins is low this caused the board to power up an reset in a mode other then default, and the board is held in reset til the code is run. the modules control pins need a voltage level maximum of 3.3 volts and the controllers output pins are at about 3 .96 volt so what if any interface id need for these to situtations if i have explained it to a point, where these conditions can be understood. any help will be most appreciated. <p>thanks in advance lexpro

[bodgy]

Well if both parts can run off of 3v then this is the best thing to do.<p>If you want to be extra sure, then a low value resistor (100 ohms or so) in series with the pins between the two chips and two diodes with one anode to the pin junction and one cathode, the other ends going to 0v and +v respectively will make sure that the voltage as seen at the controllers pins can't go below a diode drop WRT Vss.<p>First you'd have to check the data sheet for the controller to see how far below zero you can go on an input pin.<p>Colin