Hi, I'm interfacing a microcontroller with an ATAPI-cdrom through some transceivers (74HC245). When I issue a 'normal' ATA-command, all goes well. But from the moment I try to issue a packet command, nothing happens. The commands I want to use are basic: eject, play audio, pause etc...

I don't know what the problem is, as other simple non-packet commands work. I've seen the atapi-example on this site, but I don't see what I'm doing wrong. Does anyone know what kind of mistake I make? I use C to program:

/*
Ports:

Port 0 : data LSB db0 - 7
Port 2 : data MSB db8 - 15
Port 1 : command lines : A0, A1, A2: 0,1,2
/iow : 3
/ior : 4
direction transceivers at P0 & P2 : 5
CS1Fx: 7

Port 3 has some led's attached
*/

#include<at89c5131.h>
#include<intrins.h>


#define cs P1_7
#define dir P1_5
#define ior P1_4
#define iow P1_3


void wacht(){
unsigned int i;
for(i=0;i<10;i++){ // 3,75 µsec delay
_nop_();
}
}
void wacht_pakket(){
unsigned int j;
for(j=0;j<300;j++){
_nop_();
}

}
unsigned char read_status(){
unsigned char c;
P1=0x9F; //address 1F7,dir==>>mcu
dir=0; // dir ==>> mcu
_nop_();
cs=0;
_nop_();
ior=0;
wacht();
c=P0;
_nop_();
ior=1;
cs=1;
dir=1;
_nop_();
return c;
}
void check_status(){ // checks BSY-flag
unsigned char c;
unsigned char d;
unsigned char e;
e=0x80;
do{
_nop_();
_nop_();
_nop_();
_nop_();
c=read_status();
d=0x80;
d=(d & c);
}while(e == d); //as long as bsy-flag = 1
}
void select_master(){
_nop_();
check_status();
P0=0xA0; // master selected
P1=0xBE; // address 1F6 & dir ==>>cdrom
dir=1;
cs=0;
_nop_();
_nop_();
iow=0; // write
wacht();
iow=1;
cs=1;
wacht();
check_status();
_nop_();

}
void set_cylH(){
P1=0xBD; //address 1F5,dir ==>>cdrom
dir=1;
_nop_();
cs=0;
_nop_();
iow=0;
wacht();
iow=1;
cs=1;
_nop_();
}
void set_cylL(){
P1=0xBC; //address 1F4,dir ==>>cdrom
dir=1;
_nop_();
cs=0;
_nop_();
iow=0;
wacht();
iow=1;
cs=1;
_nop_();
}
void set_Byte_count_packet(){
P0=0x00;
set_cylH();
P0=0x0C;
set_cylL();
}
void set_cmdreg(){
P1=0xBF; // address 1F7, ior=1, iow=1, dir=1, cs=1
_nop_();
cs=0;
_nop_();
iow=0;
wacht();
iow=1;
cs=1;
_nop_();
}
void set_feature_for_pack(){
_nop_();
P0=0x02; // overlap: yes ; DMA: no
P1=0xB9; // address 1F1 ; dir==>>cdrom
_nop_();
cs=0;
_nop_();
iow=0;
wacht_pakket();
iow=1;
cs=1;
_nop_();
check_status();
_nop_();
}
void do_packet(){
select_master();
check_status();
_nop_();
set_feature_for_pack();
set_Byte_count_packet();
_nop_();
P0=0xA0;
set_cmdreg();
check_status();
_nop_();
}
void eject_tray(){
unsigned char c;
unsigned char d;
unsigned char e;
_nop_();
check_status();
do_packet();
_nop_();
P3_3=1;
P3_6=1;
P3_5=1;
//c=read_status();

dir=1;
P3_7=0; // LED on
P2=0xFF;
P0=0x1B;
_nop_();
P1=0xB8; //address 1F0
_nop_();
cs=0;
_nop_();
iow=0; // 1st word
wacht_pakket();
iow=1;
cs=1;
P0=0x00;
cs=0;
_nop_();
iow=0; // 2nd word
wacht_pakket();
iow=1;
cs=1;
P0=0x02;
cs=0;
wacht_pakket();
iow=0; // 3rd word
wacht_pakket();
iow=1;
cs=1;
_nop_(); // all other words are reserved
cs=0;
P0=0x00;
iow=0; // 4th word
wacht_pakket();
iow=1;
cs=1;
_nop_();
cs=0;
wacht_pakket();
iow=0; // 5th word
wacht_pakket();
iow=1;
cs=1;
_nop_();
cs=0;
_nop_();
iow=0; // 6th word
wacht_pakket();
iow=1;
cs=1;
P2=0xAA;
P0=0xAA;
wacht();
check_status();
c=read_status();
e=0xFF;
d=0xF7;
d=(c | d);
if(e!=d){P3_5=0;} //different = OK!
_nop_();
}