Two switches and two LEDs using 8051

Question

I am trying to work around a circuit and my requirement is as follows: - There are two inputs and two outputs. Each input controls an individual led. I am writing a code for this requirement using a Nuvoton MS51 based controller (Which itself is 8051 based controller). The software used for the same is Keil. Following is the code I have written-

#include "MS51.h"
void main (void)
{
    P01_INPUT_MODE;
    P03_INPUT_MODE; 
    P10_PUSHPULL_MODE;
    P00_PUSHPULL_MODE;
    while (1)
    {
        if (!(P0 & SET_BIT3))
        {
            while( !(P0 & SET_BIT3));
            P0 ^= 0x01;
        }
        if (!(P0 & SET_BIT1))
        {
            while (!(P0 & SET_BIT1));
            P1 ^= 0x01;
        }
    }
}

The problem I am facing is that both the switches are not working simultaneously but only in a sequence. The first switch will work, then the second (I am not able to use the first switch again). Is there anything wrong that I am doing in the code?

Solution: I have found the mistake I was doing. The mistake was of pull-up/pull-down of the switch. My switch is pulled down and the code that I had written corresponded to the case of a pull-up. Hence my code was being stuck in the while loop again and again, hence stopping the flow of code to the next line.

Answer 1

The code may incorrectly assume buttons being active low if they actually are active high. The code can't know that, it just looks at the bit value and it may be incorrect. But that is how the code you wrote works - if either of the button bits are low, it sits in the corresponding button loop while it is low, or in other words, until it is high again without checking for the other button. If you want it to work differently, take paper and pen and design how it should work and then write it. Rarely any software is written first without thinking how it should work.