how to write complete programs for PIC16F84A to perform the CPU will execute two tasks in parallel. The first task will be a normal program Execution loop which continuously tests an active-low switch connected to RB3. When the switch is pressed, an active-high LED connected to RB4 will turn on for 1 second (using software delay). Any switch presses while the LED is on will not be detected as the CPU is busy in the 1 second software delay. After the delay and the LED is turned off, CPU will return to testing the active-low switch. The second task will be to toggle an active-high LED connected to RA1 every 0.25 seconds. Timer0 will be configured to generate an interrupt every 0.25 seconds, and the code to toggle the LED will be placed in the ISR. Timing accuracy requirements is ±1% using 800 kHz RC oscillator.

Question

how to write complete programs for  PIC16F84A to perform the CPU will execute two tasks in parallel. The first task will be a normal program Execution loop which continuously tests an active-low switch connected to RB3. When the switch is pressed, an active-high LED connected to RB4 will turn on for 1 second (using software delay). Any switch presses while the LED is on will not be detected as the CPU is busy in the 1 second software delay. After the delay and the LED is turned off, CPU will return to testing the active-low switch. The second task will be to toggle an active-high LED connected to RA1 every 0.25 seconds. Timer0 will be configured to generate an interrupt every 0.25 seconds, and the code to toggle the LED will be placed in the ISR. Timing accuracy requirements is ±1% using 800 kHz RC oscillator.