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Trouble with 8051 uart

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adisas91

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Guys,
Am new to this forum, Please help me with this bit of code I have written for syncmos sm59r16a3,
I am actually writing this code to receive a byte of data from pc, if the data's MSB is set to one it is written to port 1 or if it is 0 it is written to port 0.
The max 232 circuit has been purchased from a store, so there's no problem with it.
Now when I turn on my MC, it automatically turns port 0 and port 1 high, irrespective of whether or not its receiving any data from the pc.
Code: 
#include<reg52.h>
unsigned char AA,BB,x;
void intiserial(void)
{
        TCON=0X00;
        TMOD=0X21; 
        SCON=0x50;
        TL1=0XFD;
        TH1=0XFD;
        TR1=1;
        ES=1;
}
void delay(unsigned int x)
{
  unsigned int i;
  for(i=0;i<=x;i++)
 { 
  TH0=0XFC;
  TL0=0X17;
  TR0=1;
  while(!(TF0==1));
  TR0=0;
  TF0=0;
  }
}

void MOTOR(void) interrupt 4
{
 EA=0;
 RI=0;
x=SBUF;
if(x&0x80)
BB=x;
else
AA=x;
delay(250);
 EA=1;// Enables interrupts
}
  void main()
  {

        intiserial();
        AA=0x00;
BB=0x00;

        EA=1;
 while(1)
 {
   P0=AA;
   P1=BB;
 }
         
}

Also am thinking of using 19200 baud rate, is it safe?
Also **broken link removed** is the link to syncmos datasheet for reference
 

You forgot to mention an important parameter.

What is your crystal/clock frequency?

BigDog
 

@adisas
1)if you have 25MHz clock then your baudrate is: 21701
2)make ports as outputs: push/pull

p.s.
try this code in Keil c debuger
 

adisas,


What compiler are you using ?
I guess the evaluation code inside MOTOR function, could have been written in a better way.

REMARKS :
1 ) Not a good idea to put a delay inside interrupt treatment function.
2 ) Put that delay, before and after core configuration routines.

+++
 
Last edited:

@bigdoggoru I am using a 11.0592 mhz crystal
@js I am actually using keil, but am confused as hell, I mean how do u give input in uart window in the simulation ? It doesn't allow me to type there like,
I have my cursor flashing in the uart window, but when I type character, doesn't appear there !! very frustrating. also, I was getting -5v on the pins.
@andre_teprom That delay thing was a typo, it was something I was trying earlier that I no longer need,I will put it after the initserial,since I will be sending data like once in every 2 seconds or so. I didnt had that delay call when I was testing though.
 

-when you start DEBUG go to PERIPHERALS and then Serial window (you will see baudrate)....
you have now: 9600 baudrate
If you want 19200 you must set SMOD1 to 1

-open serial window (View - Serial windows - UART1)
note: you must click inside window and type some character, then go to debug source windows in try step by step (F10 or F11)
 
I tried initializing RI,SBUF,P0,P1, AA,BB to 0 and it worked out, in keil. The characters still don't show in the window though, but the port value's reflect according to the input.
I will be trying this code with the MC in the evening, my friend has the circuit.

@js any reason you might think it might not work now ? I mean it works fine in keil ? I dont have net connectivity in our college lab, since we have summer vacation now.
 

as I say in topic #3
ports aren't configured as output!
see your datasheet and download keil c development tool at
http://www.keil.com/c51/devproc.asp
(free to 2k code)


ps
your datasheet:
**broken link removed**
see page 30
5. GPIO
PxM1.y PxM0.y Port output mode
0 0 Quasi-bidirectional (standard 8051 port outputs) (pull-up)
0 1 Push-pull
1 0 Input only (high-impedance)
1 1 Open drain
 
Last edited:

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