C language source code for simulating serial port

This program is written to simulate the serial port hardware mechanism. When used, a timed interrupt can be set with a time interval of 1/4 baud rate. The receiving function is called once for each interrupt, and the sending function is called once for each 4 interrupts. However, the clock does not need to be fast for the microcontroller. You should know that the time interval of each BIT of the 9600 baud rate is 104us. The time for the microcontroller to push and pop the stack once is about 20us (standard 51-core 12M crystal). So the processing time must be considered clearly. Haha. The following program is placed in the timer interrupt program function

//Receiving part
sbit JieShou_D= ;//Define receiving port
uint8 DingShiJiShu, JieShou_h;//Timing count, receiving buffer
uint16 JieShou_T;//Receiving temporary register
bit KaiShi, JieShou_b;//Start receiving standard, receiving completion flag

void JieShou(void) //Receive function, receive one bit every 4 calls
{
if((KaiShi==0) && (JieShou_D==0)) //Serial start bit arrives
{
DingShiJiShu=0; //Start timing
countKaiShi=1;
JieShou_T=0xffff; //Receive temporary register set to all 1s
}
else if((KaiShi==1) && (DingShiJiShu==1)) //2nd call, serial data sampling time arrives
{
JieShou_T >>= 1;
if(JieShou_D) JieShou_T |=0x8000;
}
else if(JieShou_T & 0x807f ==0x803f) //Receive completedJieShou_T=1xxx_xxxx_x011_1111
{
KaiShi=0;
DingShiJiShu=0;
JieShou_h = JieShou_T >> 7; //Shift right 7 bits to get serial data
JieShou_b=1;
}

if(KaiShi)
{
DingShiJiShu++; //Count +1 only when receiving
DingShiJiShu &=0x03; //Receive one bit every 4 calls
}
}

//Sending part
sbit FaSong_D= ;//define sending port
uint16 FaSong_h; //sending buffer
bit FaSong_b; //sending completion flag

void KaiShiFaSong(uint8 fs) //Set the data to be sent and start sending
{
FaSong_h = fs;
FaSong_h <<= 1;
FaSong_h |= 0x0200; //FaSong_h=0000_001x_xxxx_xxx_0
FaSong_b=0; //Send flag = 0 means sending is in progress
}

void FaSong(void) //Sending function, one bit is sent each time it is called
{
if(FaSong_h) //Sending is not completed
{
if(FaSong_h & 0x0001)
FaSong_D=1;
else FaSong_D=0;

FaSong_h >>= 1;
}
else
FaSong_b =1; //Sending completed flag = 1 means sending completed
}