serial output problem

i have encounter in a strange situation that must be solved and understand, with the help of experts or people smarter than me of course.

All i want to do is to monitor 3 bits of P3:
P3.3,P3.4,P3.5. the default state of the pins is '1'.(by pull up resistor)

i monitor (with scope) the pin Txd (P3.1) while i'm simulating the bits aforementioned.
when i set the P3.3 to 0 the output is OK=> SBUF=0x01.
but when i set the P3.4 or P3.5 then the result
of SBUF is inconstant:
P3.4=0 => SBUF=0x02(OK) and changing to SBUF=0x80(BAD) alternately.
and when i set P3.5=0 => SBUF=0x04(OK) and changing to SBUF=0x40(BAD),alternately.

it seems like the value of sbuf is shifting
according to the time that i set each bit to '0'.

please help...

#include <Reg51.h>

sbit Input1 = 0xB3;// P3.3 (INT1) bit set, Input 1
sbit Input2 = 0xB4;// P3.4 (T0)   bit set, Input 2
sbit Input3 = 0xB5;// P3.5 (T1)   bit set, Input 3

char TxOK = 0;  // Software transmission flag

void serial_IT(void) interrupt 4
{
   if (TI == 1) {       // if reception accur
      TI = 0;
      TxOK = 0; // Clear software transmission flag
      }
}

void main(){
SCON = 0x40; // 8-bit UART, BaudRate set by Timer-1
TMOD = 0x20;   // Timer1 mode 2, Timer-0 mode 1
TR0 = 0;       // turn timer0 off
TCON = 0x40;   // Start baud clock
TH1 = 0xE6;    // 1200 baud 11.0592MHz
TL1 = 0x00;
ES = 1;       // Enable Serial Int
EA = 1;       // Enable Globale Int
TI = 1;        // send buffer first

while(1){
   ACC = 0x00;
   if (Input1 == 0) {
        ACC = 0x01;
        }
   if (Input2 == 0) {
        ACC =ACC | 0x02;
        }
   if (Input3 == 0) {
        ACC =ACC | 0x04;
        }
   TxOK = 1;
   SBUF = ACC;
   while(TxOK);
   }
}

i have encounter in a strange situation that must be solved and understand, with the help of experts or people smarter than me of course.

All i want to do is to monitor 3 bits of P3:
P3.3,P3.4,P3.5. the default state of the pins is '1'.(by pull up resistor)

i monitor (with scope) the pin Txd (P3.1) while i'm simulating the bits aforementioned.
when i set the P3.3 to 0 the output is OK=> SBUF=0x01.
but when i set the P3.4 or P3.5 then the result
of SBUF is inconstant:
P3.4=0 => SBUF=0x02(OK) and changing to SBUF=0x80(BAD) alternately.
and when i set P3.5=0 => SBUF=0x04(OK) and changing to SBUF=0x40(BAD),alternately.

it seems like the value of sbuf is shifting
according to the time that i set each bit to '0'.

please help...

#include <Reg51.h>

sbit Input1 = 0xB3;// P3.3 (INT1) bit set, Input 1
sbit Input2 = 0xB4;// P3.4 (T0)   bit set, Input 2
sbit Input3 = 0xB5;// P3.5 (T1)   bit set, Input 3

char TxOK = 0;  // Software transmission flag

void serial_IT(void) interrupt 4
{
   if (TI == 1) {       // if reception accur
      TI = 0;
      TxOK = 0; // Clear software transmission flag
      }
}

void main(){
SCON = 0x40; // 8-bit UART, BaudRate set by Timer-1
TMOD = 0x20;   // Timer1 mode 2, Timer-0 mode 1
TR0 = 0;       // turn timer0 off
TCON = 0x40;   // Start baud clock
TH1 = 0xE6;    // 1200 baud 11.0592MHz
TL1 = 0x00;
ES = 1;       // Enable Serial Int
EA = 1;       // Enable Globale Int
TI = 1;        // send buffer first

while(1){
   ACC = 0x00;
   if (Input1 == 0) {
        ACC = 0x01;
        }
   if (Input2 == 0) {
        ACC =ACC | 0x02;
        }
   if (Input3 == 0) {
        ACC =ACC | 0x04;
        }
   TxOK = 1;
   SBUF = ACC;
   while(TxOK);
   }
}

Is "Nir Bohadana" the same person as "Nir boh" - who started this thread?

Your code is almost certainly doomed to failure:

while(1){
   ACC = 0x00;
   if (Input1 == 0) {
        ACC = 0x01;
        }
   if (Input2 == 0) {
        ACC =ACC | 0x02;
        }
   if (Input3 == 0) {
        ACC =ACC | 0x04;
        }
   TxOK = 1;
   SBUF = ACC ;
   while(TxOK);
   }
}

In a high-level language such as 'C', you simmply cannot rely upon any processor register such as ACC retaining its value across statements.

So your first step must be to rewrite this properly in 'C' using a local variable to store your intermediate values...

yes i'm the same person.

OK, i'll try this in a couple of minutes.

thanks.

can you write the line for me that
declare a local variable to store the bits before sending them to the SBUF.

i'm confused with unsign char ,char ....

"i'm confused with unsign char ,char ...."

What, specifically, is the confusion?

Sounds like you need a 'C' textbook?

http://www.keil.com/books/

that is waaaay too 'politically correct'

Erik

i changed my program, and still i found some
odd things..

the result are as this

send >expected output> alternate output
1...........0x01..............0x40
2...........0x02..............0x20
3...........0x03..............0xA0
4...........0x04..............0x10
5...........0x05..............0x50
6...........0x06..............0x90
7...........0x07..............0xB0

the alternate output accures when i
trigger the input bit again.

#include <Reg51.h>

sbit Input1 = 0xB3;  /* P3.3 (INT1) bit set, Input 1 */
sbit Input2 = 0xB4;  /* P3.4 (T0)   bit set, Input 2 */
sbit Input3 = 0xB5;  /* P3.5 (T1)   bit set, Input 3 */

unsigned char TxOK = 0;
unsigned char xt = 0;

void serial_IT(void) interrupt 4
{
  if (TI == 1) {
    TI = 0;
    TxOK = 0;
    }
}

/* ~~~~~~~~~~ */
/*   Main Sub */
/* ~~~~~~~~~~ */
void main(){
SCON = 0x40;
TMOD = 0x20;
TR0 = 0;
TCON = 0x40;
TH1 = 0xCC;
TL1 = 0x00;
ES = 1;
EA = 1;

TxOK = 1;
TI = 1;
while(TxOK);

while(1){
if (Input1 == 0) {
        xt = 1;
        if (Input2 == 0) {
          xt = 3;
          if (Input3 == 0) {
             xt = 6;
             }
          }
        else if (Input3 == 0) {
          xt = 4;
          }
        }
else if (Input2 == 0) {
        xt = 2;
        if (Input3 == 0) {
          xt = 5;
          }
        }
else if (Input3 == 0) {
        xt = 7;
        }
else xt = 0;

TxOK = 1;
SBUF = xt;
while(TxOK);
}
}