Communication program of PC:
The following is a simple example of how to write a communication program for Modbus ASCII mode
on a PC by C language.
#include<stdio.h>
#include<dos.h>
#include<conio.h>
#include<process.h>
#define PORT 0x03F8 /* the address of COM1 */
/* the address offset value relative to COM1 */
#define THR 0x0000
#define RDR 0x0000
#define BRDL 0x0000
#define IER 0x0001
#define BRDH 0x0001
#define LCR 0x0003
#define MCR 0x0004
#define LSR 0x0005
#define MSR 0x0006
unsigned char rdat[60];
/* read 2 data from address 2102H of AC drive with address 1 */
unsigned char tdat[60]={':'，'0'，'1'，'0'，'3'，'2'，'1'，'0'，’2'，'0'，'0'，'0'，'2'，'D'，'7'，'\r'，'\n'};
void main(){
int i;
outportb(PORT+MCR，0x08); /* interrupt enable */
outportb(PORT+IER，0x01); /* interrupt as data in */
outportb(PORT+LCR，(inportb(PORT+LCR) | 0x80));
/* the BRDL/BRDH can be access as LCR.b7==1 */
outportb(PORT+BRDL，12); /* set baudrate=9600，12=115200/9600*/
outportb(PORT+BRDH，0x00);
outportb(PORT+LCR，0x06); /* set protocol，<7，N，2>=06H，
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