8255_epp.c

_计算实用教程Visual C++6.0实用教程

/*8255_epp.c*/
     
     
/*
Set of Routines for Parallel Port expander using the Enhanced 
Parallel Port protocol for 8255-PPIO. The routines invoke EPP BIOS 
calls.
     
Dhananjay V. Gadre
*/
     
#include<dos.h>
#include<time.h>
#include<stdio.h>
#include<process.h>
#include<conio.h>
     
#define FALSE 0
#define TRUE 1
     
/*Define the Port addresses of the 8255-PPIO*/
     
#define PORT_A  0x04
#define PORT_B  0x0c
#define PORT_C  0x14
#define CON_PORT    0x1c
     
     
void far (*pointr)();
int epp_config(void);
int epp_write_block(unsigned char *source_ptr, int count);
int epp_writea_writed(unsigned char port_address, unsigned char tx_value); 
int epp_writea(unsigned char port_address);
int epp_write_byte(unsigned char tx_value);
     
     
int epp_write_byte(unsigned char tx_value) 
{
unsigned char temp_ah;
     
_AH=7;
_DL=0;
_AL=tx_value;
pointr();
temp_ah=_AH;
if(temp_ah != 0) {return FALSE;}
return TRUE;
}
     
     
int epp_writea(unsigned char port_address) 
{
unsigned char temp_ah;
_AH=5;
_DL=0;
_AL=port_address;
pointr();
temp_ah=_AH;
if(temp_ah != 0) {return FALSE;}
return TRUE;
}
     
     
int epp_writea_writed(unsigned char port_address, unsigned char tx_value) 
{
unsigned char temp_ah;
_AH=0x0c;
_DL=0;
_AL=port_address;
_DH= tx_value;
pointr();
temp_ah=_AH;
if(temp_ah != 0) {return FALSE;}
return TRUE;
}
     
int epp_config(void)
{
unsigned char temp_ah, temp_al, temp_cl, temp_ch; 
_AX=0x0200;
_DX=0;
_CH='E';
_BL='P';
_BH='P';
geninterrupt(0x17);
temp_ah=_AH;
temp_al=_AL;
temp_ch=_CH;
temp_cl=_CL;
     
if(temp_ah != 0) return FALSE;
if(temp_al != 0x45) return FALSE;
if(temp_ch != 0x50) return FALSE;
if(temp_cl != 0x50) return FALSE;
     
pointr = MK_FP(_DX , _BX);
_AH=1;
_DL=0;
_AL=0x04;
pointr();
temp_ah=_AH;
if(temp_ah != 0) return FALSE;
return TRUE;
}
     
int epp_write_block(unsigned char *source_ptr, int count) 
{
unsigned char temp_ah;
_SI=FP_OFF(source_ptr);
_ES=FP_SEG(source_ptr);
_AH=8;
_DL=0;
_CX=count;
pointr();
temp_ah=_AH;
if(temp_ah != 0) {printf("\nBlock write timeout error"); return FALSE;} 
return TRUE;
}
     
main()
{
int  ret_value, ret_val;
time_t start, end;
unsigned char buf_out[10000], rx_in;
     
clrscr();
printf("\nPort Expander using 8255-PPIO and EPP protocol\n"); 
ret_value = epp_config();
if(ret_value == FALSE) { printf("\nNo EPP BIOS"); exit(1);} 
printf("\nEPP BIOS Present");
     
     
printf("\nGenerating a Square wave on Port C bits of the PPIO");
     
printf("\nSetting address and transmitting a data byte");
     
if( epp_writea(CON_PORT) == FALSE )
{printf("\nSet address failed.."); exit(1);}
     
/*writing 0x80 to Control port puts all the three port of the 
8255 in Output mode */
if(epp_write_byte(0x80) == FALSE)
{printf("\nWrite command byte failed.."); exit(1);}
     
while(!kbhit())
{
     
     
if(epp_writea_writed(PORT_C, 0) == FALSE) 
{printf("\nWrite data byte failed.."); exit(1);}
     
     
if(epp_writea_writed(PORT_C, 0xff) == FALSE) 
{printf("\nWrite data byte failed.."); exit(1);}
     
}
     
     
/*Another way to access the 8255 data ports. Set the destination 
address once and then keeping writing data to the destination 
port*/
     
/*Set Port B Address*/
if( epp_writea(PORT_B) == FALSE )
{printf("\nSet address failed.."); exit(1);}
     
while(!kbhit())
{
     
/*write 0x00 to the Port B of the 8255*/ 
if(epp_write_byte(0) == FALSE)
{printf("\nWrite data byte failed.."); exit(1);}
     
     
/*Write 0xff to the Port B of the 8255*/ 
if(epp_write_byte(0xff) == FALSE)
{printf("\nWrite data byte failed.."); exit(1); }
     
}
     
/*Transferring data to Port B using block transfer mode*/ 
printf("\n\nWriting Data Block to the last address");
if (epp_write_block(buf_out, 10000) == TRUE ) 
printf("\nBlock write successful");
else printf("\nBlock write failed");
     
return 1;
}