Arduino 4-bit Shift Register - Wokwi ESP32, STM32, Arduino Simulator

int clk = 13;

void setup() {
  pinMode(clk, OUTPUT);
}

void loop() {
  digitalWrite(clk, HIGH);
  delay(500);
  digitalWrite(clk, LOW);
  delay(500);
}

ERC Warnings

flop1:CLK: Clock driven by combinatorial logic

flop2:CLK: Clock driven by combinatorial logic

flop3:CLK: Clock driven by combinatorial logic

flop4:CLK: Clock driven by combinatorial logic