It is responsibility of design engineer to get the most performance and capability out of the resources available in limited budget and that too for specific application requirements.While the ideas presented here are around Atmel’s 89S52 microcontroller, these can be easily used with all other types of microcontrollers without any changes and configurations. This note discusses two such techniques to save microcontroller IO lines.Usually in order interface 3×2 keys i.e. 6 keys, we will need six IO pins of microcontroller to take inputs.However, in regular practice we usually recommend using matrix scanning method to interface more keys where keys are arranged in row-column format and then can be scanned one by one. In such case, we will need 3 rows and 2 columns (or vice versa) to interface 3×2 keys as shown in figure.

Simulations and prototyping have been a very important part of the electronics industry since a very long time now. Before heading in for the actual fabrication of a dedicated hardware, everyone would want to be sure that what they are making will work the way they want it to.  Over all these years while electronics companies offered dedicated hardware in their products, it was not possible for the end user to reconfigure them to his own needs. This need led to the growth of a new market segment of customer configurable Field Programmable integrated circuits called Field Programmable Gate Arrays or FPGA.