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8051 serial port


Moderators: Ajay, Junied , abbas1707, Arun Kumar V, pdi33, Shailesh NAYAK, ۞ TPS ۞, shyam, sashijoseph

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Colin Mac

Mon Jul 28 2008, 02:47PM

Registered Member #4338

Joined: Wed Oct 10 2007, 05:46AM

Posts: 56
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I want to send characters to Hyperterminal from 8051. Please let me know if my connections and code are right.

8051 TX -> MAX232 T1in.... MAX232 T1out -> PC RX

=====

9600 baud. 11.0592 MHz. 8 bits. 1 stopbit. No parity.

CODE:

clr sm0

setb sm1

MOV TMOD, #20H

MOV TH1, #253

MOV A, PCON            

clr ACC.7              

MOV PCON, A     

mov SCON, #50H ;8b, 1stop, 1start, REN enabled

GAIN: mov SBUF, #'A' ;letter A is transmitted

HERE: jnb TI, HERE

clr TI

sjmp GAIN

end

Thanks

Arun Kumar V

Mon Jul 28 2008, 07:32PM

Registered Member #426

Joined: Sun Jan 28 2007, 11:50PM

Posts: 427
Thanked 178 times in 149 posts

Hi Mac,

the max232 connection seems to be correct, the code doesn't work bcoz you haven't started the timer1, here's the modified code:

CODE:

MOV TMOD, #20H

MOV TH1, #253

ANL PCON,#7FH  

MOV SCON, #50H ;8b, 1stop, 1start, REN enabled

SETB TR1

GAIN: MOV SBUF, #'A' ;letter A is transmitted

HERE: jnb TI, HERE

clr TI

sjmp GAIN

end

all the best !

Arun

sashijoseph

Mon Jul 28 2008, 07:32PM

Registered Member #5870

Joined: Mon Feb 04 2008, 06:26PM

Posts: 524
Thanked 124 times in 117 posts

Connections are OK.
In the code you've forgotten to start the timer (setb TR1).
Some lines are superfluous...since you've already set SCON to 50H there's no need to explicitly clr and set smo and sm1.
On reset,the PCON D7 bit is cleared automatically,so you can do away with those 3 lines as well.

EDIT : Seems Arun and I posted at the same time..

[ Edited Mon Jul 28 2008, 07:34PM ]

Let there be music........

Colin Mac

Mon Jul 28 2008, 08:54PM

Registered Member #4338

Joined: Wed Oct 10 2007, 05:46AM

Posts: 56
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ok thanks a lot guys

Colin Mac

Sun Aug 03 2008, 10:49AM

Registered Member #4338

Joined: Wed Oct 10 2007, 05:46AM

Posts: 56
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That worked. Now I'm trying to send 'A' from one micro to another to turn on a led. Can you let me know if you see a problem?

CODE:

MOV TMOD, #20H

MOV TH1, #244 ;2400

ANL PCON,#7FH  

MOV SCON, #50H ;8b, 1stop, 1start, 

SETB TR1

send:

MOV SBUF, #'A' ;letter A is transmitted

jnb TI, $

clr TI

jmp send

end

CODE:

MOV TMOD, #20H

MOV TH1,  #244  ;2400

ANL PCON, #7FH  

MOV SCON, #50H ;8b, 1stop, 1start, REN enabled

SETB TR1

setb p1.7

start:

JNB RI, $ ; wait for an entire byte to be received

CLR RI ; the receive interrupt flag is set by hardware but must be cleared by software

MOV A, SBUF; 

CJNE A, #'A', start

clr p1.7

jmp $

end