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Circuit Description

This applet shows a BCD to seven segment decoder realized with the TTL-series 7449 type circuit. It converts a 4-bit binary-coded decimal value, that is the numbers 0 to 9 coded as binary patterns 0000 to 1001, into the code required to drive a seven-segment display. The additional 'ndark' input allows to disable all outputs.

For input values between 10 to 15, the 7449-type circuit generates seemingly 'random' output values. Obviously, a simple circuit implementation was more important to the designers than showing useful output patterns (like letters 'A' to 'F'); You might compare these output values with the values generated by the seven-segment decoder demonstrated in the previous applet.