Experimental circuit based on 4040 binary adder counter

1. Manual addition experiment circuit The experiment circuit for adding using a push button switch is shown in the figure below.

2. Experimental Procedure

(1) Add 1 Experiment It is recommended to assemble the circuit on a breadboard for the experiment. The circuit can be powered by 4.5V. The 12 light-emitting diodes should be arranged in the order of Q1 to Q12, from right to left; that is, the LED output by Q1 should be installed on the far right.

As shown in the circuit diagram, the CR terminal is controlled by the pull-down resistor R1.

The CP terminal is at a low potential and the circuit is in a counting state. The CP terminal is controlled by the pull-up resistor R2. It is at a high potential. At this time, press the button AN2, and the CP terminal is grounded through R3: Since the resistance of R2 is 100k and the resistance of R3 is 1k. Therefore, the CP terminal is at a low potential at this time. The CP terminal receives a falling pulse signal, and the counter performs an addition operation; as a result, Q1 outputs a high potential. The light-emitting diode at this end is lit, indicating an output of "1". Press the plus 1 button continuously, and the counter accumulates, and the result is output by Q1~Q12 and displayed by LED1~LED12.

For example, if you press AN2 six times in succession, the result shown on the 12 LEDs is 0000 0000 01 10, which is exactly 6 in binary.

(2) Reset experiment Press the reset button AN1, and all 12 LEDs go out, indicating that the output is 0.

3. Extended experiments

From the above experimental process, we can know that to get the maximum result of the counter "1111111111111", you need to press 4095 times (212-1 times) in succession. In order to speed up the addition, a multivibrator can be used to generate counting pulses. Please design a circuit that can demonstrate automatic binary addition calculation.

●Asynchronous counter and synchronous counter

The counter is mainly used to record the number of input clock pulses, and can also realize frequency division, timing, and pulse sequence generation. There are many types of counters. According to the different clock pulse input methods, they can be divided into synchronous counters and asynchronous counters; according to the different carry systems, they can be divided into binary counters and non-binary counters.

4040 is a serial counter. It is also called an asynchronous counter. It is different from a parallel (synchronous) counter in that, in an asynchronous counter, the clocks of each level are connected in series, and the state flip of the high-order trigger can only be realized after the low-order trigger generates a carry signal (additional count) or a borrow signal (subtraction count). In a synchronous counter (such as the 4-bit binary synchronous addition counter 4518), the counting pulse is connected to the clock pulse input of each trigger at the same time. When the counting pulse arrives, each trigger is triggered at the same time.