By | September 3, 2017
Digital Clock by using seven segment displayWe used 6 GAL IC in our project, first 2 IC’s are for minutes and last two IC’s are for hours.

GAL 1 is programmed in a manner that it counts from 0 to 9 and then resets by generating a carry at pin 21.

This carry goes to the clock pin of GAL 2 which counts from 0 to 5 on each pulse provided by GAL 1.

All GAL IC’s (GAL number 2 to 4) change their state whenever they pick a carry the previous IC’s EXCEPT GAL number 1.

When the direction input (dir) is held at ground, GAL cpunts from 0 to 9 normally. But when ‘dir’ is connected to ‘fc’ (force stop carry) it only counts from 0 to 5 and resets by generating a carry.

The last 2 IC’s are for hour purpose and they are dependent on each other.
Digital Clock by using seven segment displayIf last IC is displaying 0 then GAL 5 counts from 0 to 9, but if the last IC (GAL 6) is displaying 1 GAL 5 counts from 1 to 2 only. (This is because my clock is a 12 hour clock only so 1 to 9 is illegal.

So I connected the carry of last IC with ‘dir’ of GAL 5 and developed this logic. 
A switch is provided from Vcc t0 carry pin 1 of each GAL, so carry can be provided from Vcc to adjust time yourself. High at pin changes 1 state of GAL IC.
For the clock, I used 555 timers with f = 1 Hz at GAL 1. 

Schematic Diagram: 
Learn How to Make Digital Clock by using GAL MIcrocontroller

This Project is Made by Waqar Ahmed Wajahat Ali M.Shahruk Department of Applied Physics Karachi University

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