Hey there! Let's dive into your project using the MPLAB XC8 Compiler for the PIC18F452, where you're trying to control a count variable (0-99) via RB2/RB3 keys and display it on a multi-digit 7-segment display. You mentioned the program runs mostly, and you've ruled out issues with the schematic and segment byte array—since you can [I assume you were going to note some partial functionality, like seeing digits update or detecting key presses], let's go over the most common remaining pitfalls that might be causing unexpected behavior:

• Mechanical Key Debounce
  Mechanical switches bounce when pressed/released, which can lead to multiple count increments/decrements from a single press. Fix this by adding a short delay to confirm the key state is stable, plus waiting for the key to be released before continuing. Here's a quick example for active-low keys:

  // Handle RB2 (increment)
  if(PORTBbits.RB2 == 0) {
      __delay_ms(15); // Debounce delay
      if(PORTBbits.RB2 == 0) {
          count = (count < 99) ? count + 1 : 0;
          while(PORTBbits.RB2 == 0); // Wait for key release
      }
  }
  
  // Handle RB3 (decrement)
  if(PORTBbits.RB3 == 0) {
      __delay_ms(15);
      if(PORTBbits.RB3 == 0) {
          count = (count > 0) ? count - 1 : 99;
          while(PORTBbits.RB3 == 0);
      }
  }
  

• Multiplexing Refresh Rate
  If your display is flickering or digits aren't showing clearly, your multiplexing loop might be too slow. Aim for a refresh rate of at least 50Hz (so ~20ms total per full cycle of both digits). Avoid long __delay_ms() calls in the multiplexing code—if you have other tasks, consider using a timer interrupt to handle digit switching instead.

• RB2/RB3 Port Configuration
  Double-check that RB2 and RB3 are configured as inputs. In XC8, you need to set the corresponding TRISB bits to 1:

  TRISBbits.TRISB2 = 1; // Set RB2 as input
  TRISBbits.TRISB3 = 1; // Set RB3 as input
  

  If you're relying on internal pull-up resistors, ensure the RBPU bit in INTCON2 is cleared (since PIC18F452 has weak pull-ups on PORTB that are disabled by default when RBPU is set).

• Count Variable Boundary Checks
  Make sure count stays within the 0-99 range. If you're using an unsigned char for count, decrementing when it's 0 will roll over to 255, which will display incorrect digits. The code snippet above includes checks to wrap around or clamp the value properly.

• Digit Selection & Segment Timing
  Verify your digit enable logic matches your display type (common anode vs common cathode). For example, with common cathode displays, you'll set one digit's enable pin high to activate it, output the segment data, then switch to the other digit. Ensure the segment data is stable before activating the next digit, and keep the individual digit delays short (5-10ms max) to prevent flicker.

内容的提问来源于stack exchange，提问作者psychotropix