Pic16f72 hitech C...

koolguy · Nov 28, 2013

Hi,

I am using PIC16F72 the
__delay_ms(55);
is not working showing error after removing it the code work fine for led flash/blink...?
i am using #include <htc.h> header file...

Ian Rogers · Nov 28, 2013

#define _FREQ_XTAL xxxxx

You NEED to define the clock speed...

koolguy · Nov 28, 2013

yes i have done that....

Ian Rogers · Nov 28, 2013

Show me your code.

koolguy · Nov 28, 2013

I will post in night b'coz it is at home and i think it is working in Pic16F877a....

Ian Rogers · Nov 28, 2013

No problem!! I'll wait till then

koolguy · Nov 29, 2013

here is the code.....

Code:

#include <htc.h>

__CONFIG( BOREN_OFF & PWRTE_ON & WDTE_OFF & FOSC_HS & CP_OFF );

#define _XTAL_FREQ 20000000;



void main()
    {
    TRISC = 0 ;

while(1){
PORTC=0XFF;
__delay_ms(500);
PORTC=0X00;
__delay_ms(500);

}
}

Ian Rogers · Nov 29, 2013

C:

#include <htc.h>
__CONFIG( BOREN_OFF & PWRTE_ON & WDTE_OFF & FOSC_HS & CP_OFF );
#define _XTAL_FREQ 20000000 //; <--- This semi colon  shouldn't be here

void main()
    {
    TRISC = 0 ;

    while(1){
        PORTC=0XFF;
        __delay_ms(500);
        PORTC=0X00;
        __delay_ms(500);

        }
    }

Simples!!!

koolguy · Dec 10, 2013

Hi i want to calculate delay given by this subroutine....
total 16 inst cycle taken is this right? if yes that mean 16 x .2 x10-6

Code:

DELAY MOVLW 0X01                  ;  1 inst cycle
              MOVWF count1                 ;  1 inst cycle      2
   
delay    MOVLW 0X02                     ;  1 inst cycle  2+
              MOVWF counta                    ;  1 inst cycle            
     
delay_0
             DECFSZ counta,f                 ;  2 inst cycle    2+2
             GOTO delay_0                 ;  2 inst cycle    2+
             DECFSZ count1,f                   ;  2 inst cycle   2+
             GOTO delay                        ;  2 inst cycle   2+
     
RETURN                 ;  2 inst cycle  2

koolguy · Dec 11, 2013

According to data sheet MOVlW/WF take 1 inst and GOTO /CALL/RETURN/DECFSZ take 2 instruction cycle...

jpanhalt · Dec 11, 2013

Not quite. The conditional tests take one cycle if false and two cycles if true:

John

koolguy · Dec 11, 2013

yes, it is right it is taking 1 cyle on incorrect

Delay
;19 cycles
movlw 0x06
movwf d1
Delay_0
decfsz d1, f
goto Delay_0

jpanhalt · Dec 11, 2013

RITESH KAKKAR said:
yes, it is right it is taking 1 cyle on incorrect

Code:

Delay ;19 cycles movlw 0x06 movwf d1 Delay_0 decfsz d1, f goto Delay_0 NOP ;added

I am not sure what you are saying. Is your comment a question or a statement. When D1 =0 , what do you want to happen? Presumably, this delay is a subroutine, so you need a return. That return will also add two cycles. The call also takes two cycles. I agree, it is 19 cycles from movlw to the NOP that I added.

koolguy · Dec 12, 2013

I am saying that you are correct as per your instruction cycle was right and it is taking DECFSZ 1 instruction when the contd is wrong.

jpanhalt · Dec 12, 2013

That was not a right or wrong opinion. It was in the datasheet. The program counter is advanced before fetching the instruction. If the result of the instruction requires a change to the program counter, then it seems logical that another cycle is needed.

Here are some relevant quotes from the Mid-Range MCU Family Reference Manual. The datasheet for each MCU has a similar discussion about single-cycle instructions.

PC incremented before fetching instruction (page 4-5):

Internally, the program counter (PC) is incremented
every Q1, and the instruction is fetched from the program memory and latched into the
instruction register in Q4.

Pipelining (page 4-6):

An “Instruction Cycle” consists of four Q cycles (Q1, Q2, Q3, and Q4). Fetch takes one instruction
cycle while decode and execute takes another instruction cycle. However, due to Pipelining, each
instruction effectively executes in one cycle. If an instruction causes the program counter to
change (e.g. GOTO) then an extra cycle is required to complete the instruction (Example 4-1).

John

misterT · Dec 12, 2013

Ian Rogers said:

C:

#include <htc.h>
__CONFIG( BOREN_OFF & PWRTE_ON & WDTE_OFF & FOSC_HS & CP_OFF );
#define _XTAL_FREQ 20000000 //; <--- This semi colon  shouldn't be here

void main()
    {
    TRISC = 0 ;

    while(1){
        PORTC=0XFF;
        __delay_ms(500);
        PORTC=0X00;
        __delay_ms(500);

        }
    }

Simples!!!

~~Extra semicolons are not a problem.. they do nothing.~~

EDIT: Sorry, that semicolon was in a define statement. That is a problem.

Pic16f72 hitech C...

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