adding a assembly file to project

You need to add an

RSEG PR?delay_asm?delay_asm

The easy and error proof way to do this is to first code a skeleton routine in 'C'. Then use the generated assembler as a template for your assembly code.

Erik

For such a simple loop why don't you stay in "C"

void Delay (unsigned char Cycles)
{
    while (--Cycles);
}

DELAY1: DJNZ R7,DELAY1

For such a simple loop why don't you stay in "C"
This function generates super efficient code
Maybe and maybe not depending on brand, options and release. There is absolutely no guarantee that C will generate any specific code.

Thus all timing must be in assembler.

There is no end to the bitbanging and other time critical routines I have seen fall apart because the Compiler got upgraded/replaced.

Erik

If you really want accurate timing, use a timer.

Even hand-tweaked assembler loops can fall apart the instant you change parts (12 clocks per instruction? 4? 2?), or oscillator frequency, or perhaps the external memory subsystem timing.

Any function you put in software -- in whatever language -- will leave you potentialy liable for software maintenance when the environment changes in just the wrong way.

Thanks for reply.

following was the code after modification.

EXTRN CODE (mod_delay)
PUBLIC delay_asm

code_asm  SEGMENT CODE

RSEG code_asm
using 0

delay_asm:
   mov A,R7
rv:dec A
   Jnz rv
   call mod_delay
   RET

END

Rename the label "delay_asm" to "_delay_asm" in your assembly file. The compiler wants to see a leading "_" on any function that passes parameters via registers. Since delay_asm is using r7, it needs a leading "_".

Thanks bill

code is working.
Asm routine is getting called from main
and 'C' routine from asm.
so if no parameters are passed ' _ ' is not required.

code after adding ' _ 'is:

EXTRN CODE (mod_delay)
EXTRN DATA (var_global)
PUBLIC _delay_asm

code_asm  SEGMENT CODE

RSEG code_asm
using 0

_delay_asm:
   mov A,var_global
rv:dec A
   Jnz rv
   call mod_delay
   RET

END

mov A,R7  ;take low byte of var_int to acc
..        ; logic oprns
mov A,R6  ;take high byte of var_int to acc

EXTRN DATA (var_int)
....
mov DPTR,var_int

can i write

mov DPTR,var_int

No - Although the 8051 does a decent job manipulating the 16 bit DPTR, it is an 8 bit processor and just can't do this in one instruction. The DPTR can be loaded with a constant value in one fell sweep, but not with the value contained in a variable.

Stick with:

mov A,R7 ;take low byte of var_int to acc
.. ; logic oprns
mov A,R6 ;take high byte of var_int to acc

or, if you want this value in DPTR do:

mov DPL, R7 ;DPL is low byte of DPTR
mov DPH, R6 ;DPH is high byte of DPTR

Bill

Hi Bill

since we have started discussion on
assembly <----> 'C'

why don't we discuss other issues which are related to this topic.This can be helpful to all.

Every body is invited to share different type of problems they experience while workin with C <-> Assembly.

regards
Naresh

"Every body is invited to share different type of problems they experience while workin with C <-> Assembly"

Better to make that a new thread - with a relevant Subject line.
Of course, you'd start with a link to this one!