Diode matrix

A diode matrix used in an early calculator to encode multiple key switches onto 10 signal lines. In this example, each row is connected to a key switch and energizes one of the visible copper traces. The diodes, small red cylindrical objects with wire leads, are soldered between the "row" traces visible here and the hidden "column" traces on the back side of this printed circuit board. A single key press can energize one or more wires to represent digits or functions of the calculator.

In digital electronics, a diode matrix is a two-dimensional grid of wires, with diodes connecting at selected intersections. A single row of the diode matrix is activated at any one instant. Current flows through each diode that connects to a column. These activated columns may be used as control signals for some connected system, or may represent computer data or instructions.

A diode matrix is one technique for implementing a read-only memory. It may be used as the control store or microprogram in many early computers. A logically equivalent transistor matrix is still used as the control store or microprogram or 'decode ROM' in many modern microprocessors.

This page is issued from Wikipedia. The text is available under Creative Commons Attribution-Share Alike 4.0 unless otherwise noted. Additional terms may apply for the media files.