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Serial Data Generator Schematic Circuit Diagram

Testing Circuit with Data Generator

The data generator provides a straightforward method for testing a circuit without the need for complex software. All the necessary components are easily accessible. The circuit design is structured around the timing of a Type SDA3002 circuit, utilizing a three-wire connection as opposed to the two-wire I2C format. In cases where only a single fixed data word is required, the omission of DIP switches S2 and S3, along with the eightfold pull resistor arrays, is possible. This results in the inputs of IC3 and IC4 being maintained at fixed levels. The generator’s foundation rests on two cascaded shift registers (IC3 and IC4), serving as 16-bit registers functioning in parallel with serial converters.

Clock Generation and Initialization

IC2 provides the clock, initiated by setting bistable IC1a.b with the button switch S1. Upon pressing S1, a 100-pulse is applied through the differentiating networks R1 and C1 to set the input of the bistable. The capacitor discharges via R2. It’s crucial to note that the pulse duration remains constant even when S1 is held down. This is essential to prevent timing discrepancies, as exceeding half a clock period could lead to issues. The output of IC1b serves as the enable signal for the circuit under test. The start pulse also facilitates loading the logic levels, configured with DIP switches, onto the shift registers. The registers accept parallel data as long as the signal at pin 1 is low, underscoring the necessity of a short start pulse.

Serial data generator Schematic diagram

Test Cycle Initiation and Clock Generation

The initiation of the entire test cycle is marked by the start signal. Refer to the timing diagram in Fig. 2, where output 23 of IC2 undergoes inversion by IC1d to serve as the clock source for shift registers. This arrangement ensures that D0 remains at the output for an entire clock period, lasting 1.25 ms. Upon reaching a high output 18 times, the bistable resets, and output 23 of IC1, linked to output 25 and 28 of IC2, pulls the enable line low, concluding the cycle.

Variable Bit Shifting and Bistable Addition

In this illustration, a total of 18 bits undergo shifting. The two most significant bits (MSBs) are influenced by the serial input of IC3. If this input registers as high, D16 and D17 are set to ‘1’. If flexibility is needed for these bits to be variables, one or two additional bistables connected as a shift register must be introduced. The generator’s current draw, primarily determined by the pull-down resistor, remains very low, approximately 80, when all bits are high. After the press of S1, the oscillator briefly activates, doubling the current.

Serial data generator Schematic diagram

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