Learn How to Make Digital Clock by using GAL MIcrocontroller

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
Learn How to Make Digital Clock by using GAL MIcrocontroller Learn How to Make Digital Clock by using GAL MIcrocontroller Reviewed by Abid Jamal on September 04, 2017 Rating: 5

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