Serial Communication

[anon10457]

Hi,

MOV TMOD ,#20H
MOV TH1,#-6 ; to set baud rate to 4800
MOV SCON,#50H
SETB TR1
AGAIN: MOV SBUF,#'A'
HERE: JNB TI,HERE
SJMP AGAIN
END

It displays error:

Compiling file: s13.asm
Initializing pre-processor ...
Notice at 2 in s13.asm: Overflow `-6' -> `65530'
Syntax error at 2 in s13.asm: Operand value out of range: `-6' (`65530')
Pre-processing FAILED !
Creating code listing file ... -> "s13.lst"
1 error, 0 warnings

Please guide.

Thanks,
Anon10457

[anon10457]

Hi,

Please give a hint to the above error.

Thanks,
Anon10457

[basant]

Anon10457,

The compiler is clearly saying what is wrong. What other hint do you expect from us?

-- Basant

[basant]

Anon10457,

Probably assembler doesn't like '-6'. Try giving hex equivalent.

-- Basant

[anon10457]

Hi,
In the sample code below it keeps on looping

ORG 00H
JMP MAIN
MAIN:
MOV TMOD,#20H
MOV SCON,#50H
MOV TH1,#0FDH
SETB TR1
AGAIN: MOV SBUF,#'A'
HERE: JNB TI,HERE
CLR TI
SJMP AGAIN
END

As value reaches to 655021 it keeps on looping infinite to
655021--655022--655023--655021again.
Where am I making mistake?

Thanks
Anon10457

[basant]

Anon10457,

Can you explain your observations more? Are you referring to the inner loop and saying that inner loop (for label HERE) never terminates?

-- Basant

[anon10457]

Hi,

Yes, I am talking about the HERE loop only.

Thanks,
Anon10457

[basant]

Anon10457,

I will give it a shot in the evening. Code structure looks alright though.

Thanks
Basant

[basant]

Anon10457,

I ran this program. It works fine and comes out of the inner loop once the transfer is over. Set a breakpoint at 'CLR TI' and verify yourself.

-- Basant

[anon10457]

Hi,
May I know for how long it runs for you?

Cos for me it is still in looping..655021--655022--655023--655021again.

Thanks,
Anon10457

[basant]

Anon10457,

You need to provide more information about your setup. The same program works for me, I am not sure what difference you have. Please provide the following information.

• What is your MCU?
• In which register you are seeing the values 65... and so on?
• Did you set the breakpoint at 'CLR TI' instruction and verified whether it comes out of the loop?
• Are you doing the experiment on your local machine or in VirtuQ lab?
• Also show us the screenshot of your simulation run with a breakpoint as above?

Thanks
Basant

[anon10457]

Hi,

• What is your MCU?
• In which register you are seeing the values 65... and so on?
• Did you set the breakpoint at 'CLR TI' instruction and verified whether it comes out of the loop?
• Are you doing the experiment on your local machine or in VirtuQ lab?
• Also show us the screenshot of your simulation run with a breakpoint as above?

1. MCU 8051 IDE (AT89S52)
2. Timer1 register. Values keeps on wandering and never comes out of the loop.
3. Tried with breakpoints too, but it never comes out of the loop.
4. I've tried on both, result is same.
5. I've enclosed the screenshot.

Thanks,
Anon10457

[basant]

Anon10457,

For AT89S52 also, code works fine. I think that though you have set the breakpoint, you are just doing single stepping to see whether it comes out of the loop. Since the loop has to run for long time, you get the impression that it never comes out of the loop. In this case, if you do run (Simulator -> Run (F9) ), it should reach the breakpoint. Further, just looking at the timer value is not going to help as you have set it up in auto-reload mode. That is why you keep seeing the same values.

I don't have any further inputs to give on your program. The program as such is fine, but you are not running the simulation correctly.

-- Basant