In this post, we will see how to reset the IC 74LS90 to any number from 1 to 9. To build these circuits, we need the following components:
- IC 74LS90
- A 7-segment display
- IC 74LS47 in case we use a common anode display, IC 74LS48 in case we use a common cathode display,
- IC 74LS08
Connections:
These connections are constant for all counting modes:
🔹 Pin 12 (Q0) of the 74LS90 → Pin 7 (A) of the 74LS47
🔹 Pin 9 (Q1) of the 74LS90 → Pin 1 (B) of the 74LS47
🔹 Pin 8 (Q2) of the 74LS90 → Pin 2 (C) of the 74LS47
🔹 Pin 11 (Q3) of the 74LS90 → Pin 6 (D) of the 74LS47
Counting from 0 to 1.
* On pin 14 (CKA) we connect the clock signal.
* The pins 2 (R0(1)), 3 (R0(2)), 6 (R9(1)), 7 (R9(2)) are grounded.
Counting from 0 to 2.
* On pin 14 (CKA) we connect the clock signal.
* The pins: 6 (R9(1)), 7 (R9(2)) are connected to ground.
* We connect pin 2 (R0(1)) to pin 9 (Q1).
* We connect pins 1 (CKB) and 3 (R0(2)) to pin 12 (Q0).
Counting from 0 to 3.
* On pin 14 (CKA)we connect the clock signal.
* The pins: 6 (R9(1)), 7 (R9(2))are connected to ground.
* We connect the pins 2 (R0(1)) and 3 (R0(2)) with pin 8 (Q2).
* We connect the pins 1 (CKB) with pin 12 (Q0).
Counting from 0 to 4.
* At pin 14 (CKA) we connect the clock signal.
* The pins: 6 (R9(1)),7 (R9(2)) are connected to ground.
* We connect pin 2 (R0(1)) with pin 8 (Q2).
* We connect the pins 1 (CKB) and 3 (R0(2)) with pin 12 (Q0).
Counting from 0 to 5.
* At pin 14 (CKA) we connect the clock signal.
* The pin, 7 (R9(2)) is connected to ground.
* We connect pins 2 (R0(1)) and 6 (R9(1)) with pin 8 (Q2).
* We connect pin 1 (CKB) with pin 12 (Q0).
Counting from 0 to 6.
* On pin 14 (CKA) we connect the clock signal.
* The pins 6 (R9(1)) and 7 (R9(2)) are connected to ground.
* We connect pin 2 (R0(1)) to pin 8 (Q2).
* We connect pin 1 (CKB) to pin 12 (Q0).
* We add an AND gate, connecting pins 12 (Q0) and 9 (Q1) to its inputs, and its output we connect to pin 3 (R0(2)).
Counting from 0 to 7.
* On pin 14 (CKA) we connect the clock signal.
* The pins 6 (R9(1)) and 7 (R9(2)) are grounded.
* We connect the pins 2 (R0(1)) and 3 (R0(2)) to pin 11 (Q3).
* We connect pin 1 (CKB) to pin 12 (Q0).
Counting from 0 to 8.
* On pin 14 (CKA) we connect the clock signal.
* The pins 6 (R9(1)) and 7 (R9(2)) are grounded.
* We connect the pins 1 (CKB) and 3 (R0(2)) with pin 12 (Q0).
* We add an AND gate, connecting the pins to its inputs 11 (Q3) and Vcc (5v) ,its output we connect to pin 2 (R0(1)).
Counting from 0 to 9.
* At pin 14 (CKA) we connect the clock signal.
* The pins 2 (R0(1)), 3 (R0(2)), 6 (R9(1)), 7 (R9(2)) are connected to ground.
* We connect pin 1 (CKB) with the pin 12 (Q0).
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