sending string with parity

The 8052 does not do parity
it does; however there is no means of using that feature in C.

When parity is required, I just write the ISR in assembler and take advantage of the 'P' bit.

Erik

The 8052 does not do parity
it does; however there is no means of using that feature in C.

When parity is required, I just write the ISR in assembler and take advantage of the 'P' bit.

Erik

Correct me if I'm wrong (and I'm not feeling too chipper today), but a way to control the parity of the transmitted byte can be done in "C" and does not require an assembly source file. (Seriously, correct me if I'm wrong).

By assigning the ACC with the byte to be transmited, the PSW is updated.

A direct ACC = Byte_Value will load the accumulator with the value without [executable] side effects.

The PSW contains the a parity bit in the bit-addressable and defined sbit "P". This bit can then be transfered into the 9th bit by assigning the pre-defined sbit "TB8" the correct value for parity for your odd/even requirements.

#define PARITY_STATUS   P   // "P" is a pre-defined bit in the PSW SFR for parity.
                            // (I'm just giving it a better name that just P)
    // bit     parity;
    // u8 data the_byte;
    // ...pre-code

    ACC    = the_byte; // Actually loads the ACC with no side effects
                       // (YOU MUST check the resulting code to make sure
                       //  that your data-stores behave similarly)

    parity = PARITY_STATUS; // Set to 1 when the ACC contains
                            // an odd number of 1 bits

    if( parity == 1 ) // based upon the P status, assign your 9th bit
    {
        TB8 = 1; // either 1 or 0 depending upon your parity requirements
    }
    else
    {
        TB8 = 0;
    }

    SBUF = the_byte; // then send your byte out

    // post-code...

Generates the following assembly code:

; FUNCTION Send_With_Parity (BEGIN)

          MOV     A,the_byte

          MOV     C,P
          MOV     parity,C

          JNB     parity,?C0050


          SETB    TB8

          SJMP    ?C0051
?C0050:
          CLR     TB8
?C0051:
          MOV     SBUF,the_byte

          RET

; FUNCTION Send_With_Parity (END)

It is best to inspect the compiler's output to ensure this is working in your own application.

--Cpt. Vince Foster
c/o VRWC (founding member)
2nd Cannon Place
Fort Marcy Park, VA

This is the code to send with parity
i tesed on the hyper terminal and it work great !!

sending:

ACC = in_string[i]; // P = Even
TB8 = ~P; // ~p = Odd
SBUF = ACC;
while (! TI); // while (TI == 0);
TI = 0;

reciving :

while (RI == 0); // while (! RI);
RI = 0;
ACC = SBUF;
RB8 = P;
input_line[i] = ACC;

mayer

I would not use the ACC to make an assignment to a variable: don't use ACC as an rvalue...

sending:

ACC = in_string[i]; // P = Even
TB8 = ~P; // ~p = Odd
SBUF = in_string[i]; // changed from ACC
while (! TI); // while (TI == 0);
TI = 0;

reciving :

while (RI == 0); // while (! RI);
RI = 0;
temp = SBUF;
ACC = SBUF;
RB8 = P;
input_line[i] = temp; // changed from ACC

You aren't too sure what the actual accumulator (ACC) will contain by the time you choose to use it as an rvalue. "ACC" is not to be treaded like a 'normal' variable.

--Cpt. Vince Foster
c/o VRWC (founding member)
2nd Cannon Place
Fort Marcy Park, VA

Oops..

while (RI == 0); // while (! RI);
RI = 0;
temp = SBUF;
ACC = temp;

it does; however there is no means of using that feature in C.

Every time this subject comes up on the forum you state that it cannot be done in 'C', in spite of it being well documented in the Keil knowledge base. You have even been corrected on the forum by a member of Keil staff.

Why, then, do you persist in posting this misinformation?

In the forlorn hope that you might actually read some documentation and learn something here is a link:

http://www.keil.com/support/docs/1619.htm