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ศาสตราจารย์์ ดร.มงคล เดชนครินทร์ 241

//Page 3/4 of Fig. 7 //Page 4/4 of Fig. 7

//Wait for upld signal from uC 8088 (XmtFlg=1) //Read RB1 pin for 2 consec. pulse times
cnt1 = 0; //clear counter of wait time ch3 = PORTB & 0x02; //pin RB1 logic value #1
while(XmtFlg == 0) Delay_ms(1); //1-ms delay=>2nd bit after SP
{ Delay_ms(10); ch4 = PORTB & 0x02; //pin RB1 logic value #2
cnt1++; //count time
if (cnt1 == 100) break; //quit after 1 sec //Check for data/control bit
} //end while if (ch3 != 0x00) //=> "1" bit or start bit
{ if (ch4 != 0x00) //it's start bit
if (XmtFlg != 0) //start sending data bytes { if (IntFlg == 0) {IntFlg = 1;};}
{ XmtFlg = 0; //reset flag => no repeat //IntFlg=0 => 1st-time INT from 8088
PORTB.F3 = 1; //pin RB3 LED on else if (ch4 == 0x00) //it's "1" bit
Delay_ms(500); { if (IntFlg == 0) {IntFlg = 1;}
//1st-time INT from 8088
//STORE DATA BYTES 0x01-0x80 in buffer else if (IntFlg != 0)
buf[0]=0x01; buf[1]=0x02; buf[2]=0x04; //not 1st-time INT from 8088
buf[3]=0x08; { ch2 = ch2 << 1; //regular data bit
buf[4]=0x10; buf[5]=0x20; buf[6]=0x40; ch2++; //add 1 to LSb
buf[7]=0x80; };
}; //end if ch4
//send 8 bytes to uC 8088, last byte first }
for (cnt=7; cnt >= 0; cnt--) else if (ch3 == 0x00) //=> "0"/stop bit
{ ch0 = buf[cnt]; { if (ch4 == 0x00) //it's "0" bit
//display and send data byte { if (IntFlg == 0)
ShwSnd(ch0, 1); //first-time INT from 8088
} //end for { XmtFlg = 1; //set xmit flag
IntFlg = 1; //set INT flag
//send 5 consec. 0xFF's to conclude sending } //end if IntFlg
for (cnt=0; cnt<5; cnt++) else if (IntFlg != 0) //later INT
{ ShwSnd(0xFF, 1); }; { ch2 = ch2 << 1; }
//shift ch2 but no increase
} //end if XmtFlg }
else if (ch4 != 0x00) //it's stop bit
//Loop until reset { buf[dcnt] = ch2; //store char in buf
while(1) {}; dcnt++; //prepare to store next char
} //end main
//******************************************* //display complete data byte (for debug)
PORTA = (ch2 & 0x0F) << 1;
void senbyt(unsigned char ch) PORTB = ch2 & 0xF0;
{//send data byte in ch Delay_ms(250); //On-time
unsigned char mask, ch1; PORTA = 0x00; PORTB = 0x00;
int i; Delay_ms(64); //Off-time
//send start bit //watch for 5 consec. 0xFF's
senstrt(); if (ch2 == 0xFF) {ecnt++;}
else if (ch2 != 0xFF) {ecnt = 0;};
//send 8 regular data bits in ch, MSb first //reset end counter
mask = 0x80; //take MSb first if (ecnt == 5) //end of receive
for (i=0; i<8; i++) {
{ dcnt1 = dcnt; ecnt1 = ecnt;
ch1 = ch & mask; //select bit to send //save counters
if (ch1 != 0x00) dcnt = 0; ecnt = 0;
{ onebit(); } //send hi via RA0 //reset counters
else if (ch1 == 0x00) } //end if ecnt
{ zrobit(); }; //send lo via RA0 ch2 = 0x00; //prepare for new dat byte
mask = mask >> 1; //select next lower bit }; //end else if ch4
} //end for i }; //end else if ch3

//send stop bit INTCON = 0B10010000;
senstop(); //GIE=1 + INTE=1 => enable INT
} //end senbyt OPTION_REG = 0B01000000;
//******************************************* //INTEDG=1 => rising edge trig.

void interrupt(void) //ext. INT via RB0 (pin 6) } //end interrupt
{//receive data byte in ch2 //*******************************************
unsigned char ch3, ch4;
INTCON = 0x00; //prevent further interrupt
//Identify bit 'start,' 'regular,' or 'stop'
Delay_us(500); //0.5-ms delay, skip sync pls
Delay_ms(1); //1-ms delay=>1st bit after SP

ภาพท่� ๗ ซึ่อฟตั์แวร์การแลกเปล้�ยนี้ข้้อมูลแบบข้ัดจังหวะข้องไมโครคอนี้โทรลเลอร์ PIC16F627A (ตั่อ)