I/O Ports

I/O Ports Specs Atmeg16 has 32 I/O ports (Ports A, B, C, D 8 lines each). Each output buffer has symmetrical drive characteristics with both high sink and source capability. The pin driver is strong enough to drive LED displays directly. All port pins have individually selectable pull-up resistors. All I/O pins have protection diodes to both VCC and Ground.

Port Registers 3 registers are dedicated to each port. So for example Port A has the following 3 bytes (control I/O registers) controlling its operation: DATA Reg.  Direction Reg. Pin Reg. 0->input pin 1->output pin

Ports’ Ssetting by CodeVision Wizard

I/O port and alternate functions

I/O port and alternate functions Pullup is enabled lf: Pullup-override w. value 1 OR write port a 1 and write direction 0 (input) together w. PUD (pullup disable in I/O Register SFIOR=0)

Most port pins have alternate functions in addition to being General Digital I/Os (see pin assignment). PVOExn: Pxn PORT VALUE OVERRIDE ENABLE PVOVxn: Pxn PORT VALUE OVERRIDE VALUE

? Assignment: Design an Electronic Lock with arbitrary specs e.g.: 3 digits Alarm after 3 trials Master key