Source: https://mokxi.com/parts/74hc74 Updated: 2026-09-27 Part # 74HC74 dual flip-flop Two D flip-flops with preset and clear. Divide a clock with one. or see every part - 14 pins Drawn live by the editor's own code, at the size you see it. Reference ## Every one of its 14 pins Pin Role What it does 1RD Input 1D Input 1CP Input 1SD Input 1Q Output 1QN Output GND Input or output 2QN Output 2Q Output 2SD Input 2CP Input 2D Input 2RD Input VCC Input or output This part ## What it does The 74HC74 packages two independent D-type flip-flops, each with a data input, a clock, and an active-low set and reset that both act immediately rather than waiting for a clock edge. Pull reset low and the flip-flop clears; pull set low and it presets; do both at once and the datasheet calls the result unstable, since the outputs briefly stop being complements of each other until one input is released. The clock is positive-edge triggered: whatever is on the data pin at the instant the clock rises is what the flip-flop latches, and nothing it does in between edges matters at all. That single behavior, one bit remembered from one edge, is the entire building block a binary counter is made from: feed a flip-flop’s complementary output back into its own clock and it divides whatever is driving it by two, and chaining a few of them is how the ripple counter template on this site counts. How it is modeled ## What is true about the 74HC74 dual flip-flop, here ### 74HC74: dual D-type flip-flop with set and reset Two independent positive-edge-triggered flip-flops. Each has a data input (nD), a clock (nCP), an active-low set (nSD) and an active-low reset (nRD), presenting both nQ and its complement. SD and RD are asynchronous and beat the clock; the clock only matters on a clean Low-to-High edge, and an edge that arrives while the supply is still settling is not counted as one, which is what stops a ripple counter from latching Unknown forever at power-on. A real flip-flop powers up random; this one powers up cleared (Q low), because a divider fed Unknown would never escape it. Propagation delay: 14 ns typical, from CP, SD or RD to Q or QN. See it in: Binary counter. ### Not modeled One typical delay, and nothing around it. Each chip carries a single propagation delay taken from its datasheet's typical column at VCC = 5 V, CL = 15 pF and 25 °C, and uses it for every path through the package. There is no minimum or maximum, no spread between the gates in one chip, no rise or fall time, no output slew and no dependence on supply voltage, load capacitance or temperature, all of which a real 74HC part has, and all of which a datasheet gives ranges for. On the 74HC595 the one figure is the STCP-to-Qn number used for SHCP and MR to Q7S as well, which the datasheet lists a nanosecond or two apart. No setup, hold or pulse-width checks. The 74HC74 and the 74HC595 take a clock edge whenever they see one; nothing here refuses data that changed too close to the edge or a clock pulse that was too narrow, and nothing warns about it. A real part would metastable or simply miss. No supply current, no output current limit and no bus contention damage. An output driving into another output is resolved as two drivers on one net; nothing gets hot. Sequential parts power up cleared rather than random, because a toggle divider fed Unknown never escapes it. See how faithfully a part behaves. From The 74HC logic family, in full. Projects ## See the 74HC74 dual flip-flop in a project Learn ## Where it turns up in a lesson ### In the twelve week course - Week 7: Memory: flip-flops and counters ### In a learn article - Multisim Live Is Gone: A Chromebook Alternative - Flip-Flops Explained: SR Latch, D and JK Flip-Flops More parts ## The rest of the bench Every one of these is drawn and simulated the same way. Full-size breadboard A real 0.1 inch grid with the rails and the center channel, 63 columns wide. Jumper wires Drag from any pin or hole to any other. Corners snap, and you can drag them. Power A supply rail at the voltage you choose. Ground The other end of every circuit. LED Lights when current flows. Five colors, and the brightness is what your eye would see. Resistor Any value you like, with the color bands drawn to match. ESP32-C3-DevKitM-1 A RISC-V board that runs your firmware at 160 MHz on the real memory map. Pushbutton A 12 mm tactile switch. Hold it while the simulation runs. Raspberry Pi Pico The RP2040 board on our own Cortex-M0+ core. Pick a program and press Run. Raspberry Pi Pico W Raspberry Pi Pico W (RP2040). The same board and the same pinout as a Pico, with the CYW43439 on it. The WiFi is simulated (no radio, no real internet), and the on-board LED, which hangs off that chip rather than off GP25, is driven through the same path. Everything else is the Pico. STM32F411 Black Pill The Black Pill on our own Cortex-M4 core. Pick a program and press Run. BBC micro:bit V2 The nRF52833 board with its 5x5 LED matrix, buttons A and B and a speaker. Wire the rings to a breadboard. See every part ## Wire up the 74HC74 dual flip-flop Open the editor and push it into the breadboard. It is free, and it runs on your own machine. Start building Open the editor