STC89C52_51 MCU_Serial port configuration_UART serial communication

Register Configuration

PCON Power Management Register

Bit number D7 D6 D5 D4 D3 D2 D1 D0

Bit Symbol SM0 SM1 SM2 REN TB8 RB8 TI RI

– Mode Mode Mode 1 directly clears Enable serial port reception Mode 1 receives stop bit Send flag bit, cleared by software Receive flag bit, cleared by software

//Cannot bit address

SCON serial port control register

Bit number D7 D6 D5 D4 D3 D2 D1 D0

Bit Symbol SM0 SM1 SM2 REN TB8 RB8 TI RI

– Mode Mode Mode 1 directly clears Enable serial port reception Mode 1 receives stop bit Send flag bit, cleared by software Receive flag bit, cleared by software

/* DISCON */

sbit SM0 = SCON^7;

sbit SM1 = SCON^6;

sbit SM2   = SCON^5;

sbit REN   = SCON^4;

sbit TB8   = SCON^3;

sbit RB8   = SCON^2;

sbit TI = SCON^1;

sbit RI    = SCON^0;

Mode & Baud Rate (Song Xuesong P183)

SCON mainly uses mode 1, the baud rate

Correspondingly, use mode 2 of timer T1 & T2

TH1 = TL1 = 256 - Crystal value/12/2/16/Baud rate

(256 is the overflow value of TL1, 12 refers to 12 clock cycles, and 16 is the hardware factor)

SBUF

Two SBUF registers, responsible for receiving and sending buffers respectively

process

Configure the serial port to mode 1

Configure timer T1 to mode 2

Calculate the value of TH0&TL0 according to the baud rate

Configure PCON & SCON registers

Turn on the timer

IO port simulates UART serial communication

Schematic diagram of UART serial port data transmission

Digging a hole: How are the baud rate & TH0 calculated?

#include

sbit PIN_RXD = P3^0;

sbit PIN_TXD = P3^1;

bit RxdOrTxd = 0;

bit RxdEnd = 0;

bit TxdEnd = 0;

unsigned char RxdBuf = 0;

unsigned char TxdBuf = 0;

void configUART(unsigned long baud);

void startRXD(void);

void startTXD(unsigned char dat);

void main(void)

{

EA = 1;

configUART(9600);

while(1)

{

while(PIN_RXD);

startRXD();

while(!RxdEnd);

startTXD(RxdBuf+1);

while(!TxdEnd);

}

}

void configUART(unsigned long baud)

{

TMOD &= ~(0xF<<0);

TMOD |= 0x1<<1;

TH0 = 256 - (11059200 / 12) / baud;

}

void startRXD(void)

{

TL0 = 256 - ((256 - TH0) >> 1);

ET0 = 1;

TR0 = 1;

RxdEnd = 0;

RxdOrTxd = 0;

}

void startTXD(unsigned char dat)

{

TxdBuf = dat;

TL0 = TH0;

ET0 = 1;

TR0 = 1;

PIN_TXD = 0;

RxdEnd = 0;

RxdOrTxd = 1;

}

void timer0(void) interrupt 1

{

static unsigned char cnt = 0;

if(RxdOrTxd)

{

cnt++;

if(cnt<=8)

{

PIN_TXD = TxdBuf & 0x01;

TxdBuf >>= 1;

}

else if(cnt==9)

{

PIN_TXD = 1;

}

else 

{

cnt = 0;

TR0 = 0;

TxdEnd = 1;

}

}

else

{

if(cnt==0)

{

if(!PIN_RXD)

{

RxdBuf = 0;

cnt++;

}

else

{

TR0 = 0;

}

}

else if(cnt<=8)

{

RxdBuf >>= 1;

if(PIN_RXD)

{

RxdBuf |= 0x80;

}

cnt++;

}

else

{

cnt = 0;

TR0 = 0;

if(PIN_RXD)

{

RxdEnd = 1;

}

}

}

}

UART serial communication

Teaching Edition

#include

void configUART(unsigned long baud);

void main(void)

{

configUART(9600);

while(!RI);

RI = 0;

SBUF = SBUF + 1;

while(!IF);

IF = 0;

}

void configUART(unsigned long baud)

{

SCON = 0x50;

TH1 = 256 - (11059200 / 12 / 2 / 16) / baud;

TL1 = TH1;

TMOD &= ~(0xF<<4);

TMOD |= 0x2<<4;

ET1 = 0;

TR1 = 1;

}

Industrial Edition

#include

void configUART(unsigned long baud);

void main(void)

{

EA = 1;

configUART(9600);

while(1);

}

void configUART(unsigned long baud)

{

SCON = 0x50;

TH1 = 256 - (11059200 / 12 / 2 / 16) / baud;

TL1 = TH0;

TMOD &= ~(0xF<<4);

TMOD |= 0x2<<4;

ET1 = 0;

EN = 1;

TR1 = 1;

}

void UART(void) interrupt 4

{

if(RI)

{

RI = 0;

SBUF = SBUF + 1;

}

if(TI)

{

IF = 0;

}

}

The computer sends data and displays it in the digital tube

#include

sbit road = P2^7;

sbit want = P2^6;

unsigned char code weitable[6] = 

{

~0x20,~0x10,~0x08,~0x04,~0x02,~0x01

};

unsigned char code duantable[16] = 

{

0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,

0x7F,0x6F,0x77,0x7C,0x39,0x5E,0x79,0x71

};

unsigned char ledbuff[6] = 

{

0x00,0x00,0x00,0x00,0x00,0x00

};

unsigned char T0RH = 0,T0RL = 0;

unsigned char RxdByte = 0;

void configtimer0(unsigned char ms);

void configUART(unsigned long baud);

void main(void)

{

EA = 1;

configtimer0(1);

configUART(9600);

while(1)

{

ledbuff[0] = duantable[RxdByte & 0x0F];

ledbuff[1] = duantable[RxdByte >> 4];

}

}

void configtimer0(unsigned char ms)

{

unsigned long tmp;

tmp = 11059200 / 12;

tmp = (tmp * ms) / 1000;

tmp = 65536 - tmp;

tmp = tmp + 12;

T0RH = (unsigned char)(tmp>>8);

T0RL = (unsigned char)tmp;

TH0 = T0RH;

TL0 = T0RL;

TMOD &= ~(0xF<<0);

TMOD |= 0x1<<0;

ET0 = 1;

TR0 = 1;

}

void configUART(unsigned long baud)

{

TH1 = 256 - (11059200 / 12 / 2 / 16) / baud;

TL1 = TH0;

SCON = 0x50;

TMOD &= ~(0xF<<4);

TMOD |= 0x2<<4;

ET1 = 0;

EN = 1;

TR1 = 1;

}

void ledscan(void)

{

static unsigned char i = 0;

P0 = 0x00;

want = 1;

want = 0;

P0 = wideable[i];

wei = 1;

wei = 0;

P0 = ledbuff[i];   

want = 1;

want = 0;

if(i<5)

i++;

else

i = 0;

}

void timer0(void) interrupt 1

{

TH0 = T0RH;

TL0 = T0RL;

ledscan();

}

void UART(void) interrupt 4

{

if(RI)

{

RI = 0;

RxdByte = SBUF;

SBUF = RxdByte;

}

if(TI)

{

IF = 0;

}

}