sending msg

Random guesses:

- The driver eats the first 8 characters of any message.

- The modem has a delay after you tell it to "send" while it's ignoring incoming data, but the driver is blasting away anyway; this delay happens to be 8 character times.

- The caller is bugged, and is actually passing in a pointer deeper into the message string than you think.

With no information on the code, the hardware, or what you've already tried to diagnose, it's hard to suggest anything.

Random guesses:

- The driver eats the first 8 characters of any message.

- The modem has a delay after you tell it to "send" while it's ignoring incoming data, but the driver is blasting away anyway; this delay happens to be 8 character times.

- The caller is bugged, and is actually passing in a pointer deeper into the message string than you think.

With no information on the code, the hardware, or what you've already tried to diagnose, it's hard to suggest anything.

Actually, a common mistake when attempting to send SMS messages programatically is not to wait for the prompt after issuing the AT command.

So that "random guess" could well be right!

Sorry for incomplete information here is a part of code its only part of not whole so let me know if thats insufficient:

unsigned char *Ack_ON1="Device iDevice is turned ON$";           //1st 8 chars. are not xmitted
unsigned char *at_cmgs = "at+cmgs=\"+9199xxxxxxxx\"$";  //to send ack to this no.

Cmd(at_cmgs);
CR();
XMIT(Ack_ON1);
Cnt_Z();


void XMIT(unsigned char *msg)
 {
  unsigned char i;
  i = 0;
  do
   {
    ACC = msg[i];
    SBUF = ACC;
    while(TI == 0){}
        TI = 0;
        i++;
   }
  while(msg[i] != '$');
  return;
 }

void Cmd(unsigned char *at_command)
 {
  unsigned char i;
  i = 0;
  do
   {
    ACC = at_command[i];
    SBUF = ACC;
    while(TI == 0){}
        TI = 0;
        i++;
   }
  while(at_command[i] != '$');
  return;
 }

void CR(void)
  {
   SBUF = 0x0D;           //0x0D CR
   while(TI == 0){}
   TI = 0;
   return;
  }

 void Cnt_Z(void)
  {
   SBUF = 0x1A;
   while(TI == 0){}
   TI = 0;
   return;
  }

I hope this much would be sufficient what else i've done in code is
i. receiving the msg
ii. verifying it
iii. taking action
iv. sending acknowledgment msg

    ACC = msg[i];
    SBUF = ACC;

You simply cannot use ACC in 'C' like that!

You have absolutely no guarantee whatsoever that the compiler won't have used the Accumulator for its own purposes between those two lines!!

In fact, as you're indexing arrays, it is quite likely that the compiler will have used the Accumulator for its own purposes!

In fact, it is entirely pointless - you can just write

    SBUF = msg[i];

You're not in assembler now!

I suggest you spend some time reviewing the example programs:
http://www.keil.com/download/list/c51.htm

And possibly some books:
http://www.keil.com/books/8051books.asp

Thanks Andy I will look to it and will let you know

About these books do I need to go through all of them or can you suggest me which are best and absolutely necessary mainly for C and embedded (right from 8051 to more complex architecture)

one more thing can I see assembly code in uVision just because I'm curious and if required how to add assembly code in my C program. I can work on C or assembly but not assembly and C at a same time

Hi Andy I surely didn't read any of those books but I've removed all intermediate ACC but still the same problem exists i.e. 1st 8 characters are missing anyway I'll continue some more debugging

Why do you use a dollar sign at the end of the strings? Anything wrong with using the zero-termination that is already available in the strings?

Not at all just used to do that way from my college days Now can't remember how to use 0 termination i guess "<string>",0 please correct me if I'm wrong

There is (almost) always a hidden zero at the end of C strings.

So you can just check if str[i] == 0 to detect when you have reached the end.

The only exception where a string does not contain the zero, is if you assign the string to an array that just has room for the characters but no termination, i.e.

char buf[] = "hello"; // 5 characters + termination
char buf[6] = "hello"; // 5 characters + termination
char buf[5] = "hello"; // 5 characters but no room for termination

Thanks I'll try it