6. Alarm generator

1.  Experimental task: 
Use P1.0 to output 1KHz and 500Hz audio signals to drive the speaker as an alarm signal. The 1KHz signal is required to sound for 100ms and the 500Hz signal is required to sound for 200ms, alternately. P1.7 is connected to a switch for control. When the switch is closed, the alarm signal sounds, and when the switch is opened, the alarm signal stops. Write a program.
2.  Circuit diagram 

Figure 4.6.1 3.  Hardware connection on the system board 
(1. Connect the P1.0 port in the "MCU system" area to the SPK IN port in the "Audio amplifier module" area with a wire;
(2. Connect an 8-ohm or 16-ohm speaker to the SPK OUT port in the "
Audio amplifier module" area; (3. Connect the P1.7/RD port in the "MCU system" area to the K1 port in the "Four-way toggle switch" area with a wire;
4.  Program design content 
(1. Signal generation method
500Hz signal period is 2ms, signal level reverses once every 1ms, 1KHz signal period is 1ms, signal level reverses once every 500us;
  
5.  Program flowchart 
start
Is K1 pressed?
Is FLAG=0?
Set to 200 counts
P1.0 output inversion
Delay 500us
Is the count complete?
FLAG inversion
Set to 200 counts
P1.0 output inversion
Delay 1ms
Is the count complete?
FLAG inversion
  Figure 4.6.2 6.  Assembly source program 
FLAG BIT 00H 
                                      ORG 00H 
START: JB P1.7,START 
                                      JNB FLAG,NEXT 
                                      MOV R2,#200 
DV: CPL P1.0 
                                      LCALL DELY500 
                                      LCALL DELY500 
                                      DJNZ R2,DV 
                                      CPL FLAG 
NEXT: MOV R2,#200 
DV1: CPL P1.0 
                                      LCALL DELY500 
                                      DJNZ R2,DV1 
                                      CPL FLAG 
                                      SJMP START 
DELY500: MOV R7,#250 
LOOP: NOP 
                                      DJNZ R7,LOOP 
                                      RET 
                                      END 
7．  C language source program 
#include  
#include  
  
bit flag; 
unsigned char count; 
  
void dely500(void) 
{ 
  unsigned char i; 
  for(i=250;i>0;i--) 
    { 
      _nop_(); 
    } 
} 
  
void main(void) 
{ 
  while(1) 
    { 
      if(P1_7==0) 
        { 
          for(count=200;count>0;count--) 
            { 
              P1_0=~P1_0; 
              dely500(); 
            } 
          for(count=200;count>0;count--) 
            { 
              P1_0=~P1_0; 
              dely500(); 
              dely500(); 
            } 
        } 
    } 
}