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Mix C&Assembly with Keil C51/A51

I am having a difficult time combining C and assembly in the Kiel development environment. I have a progtram which is mainly in C. I have assembly modules which are inline code. The assembly modules have to access variables which are defined in the main C area. I am using the EXTRN command in my inline ASM area for at least one char variable. ex: EXTRN DATA(curSector)

I now have an unsigned long which was being passed to the inline assembly in the Registers. That works, of course. But I wanted to directly address the long variable in my assembly code to eliminate the need to prep the registers prior to the call.

so I have

unsigned long burnAddress ; defined in the C code

in the inline assembly I have:

EXTRN DATA (burnAddress)

and I access it like this:

mov a,burnAddress ; MSB .. mov a,burnAddress +1 .. mov a,burnAddress +2 .. mov a,burnAddress +3 LSB

Is this correct?

Thanks

eng

Reply to
Nappy
Loading thread data ...

Yes.

A long needs four bytes, but the accumulator fits only one at a time, so you need four fetches.

--

Tauno Voipio
tauno voipio (at) iki fi
Reply to
Tauno Voipio

are

main

assembly in

the

:)

Yes. I was asking about the proper connection for the linker. As it seems I am not getting the proper values in the assembly.

Thanks.

Reply to
Nappy

In article , Nappy writes

Try:

unsigned long data burnAddress;

unless you are already compiling in the SMALL model.

Reply to
Stephen

or you can use unsigned long idata burnAddress; what are the errors or problems you are getting? i mean can you plz be more specific bout them. so that i can help you in a better way ;-) reagards, ajay bhargav

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Reply to
Rickey

Rickey wrote: >

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Reply to
Chuck F.

Oh Please Chuck..

Reply to
Nappy

I am trying to milk every nanosecond of speed out of a design and I have a routine which is currently being passed a LONG in registers. And I was looking to remove the time it took to load them prior to the call. So I am attempting to access the long in the routine as:

mov a,burnAddress .. mov a,burnAddress+1

etc.

But I am getting the wrong data.

When using inline assembly with uVision I can not get the CODE in the listings so suppose I have to inspect the opcodes in the hex file..

The default data area for this variable would be DATA.

Reply to
Nappy

oh plz chk. what a petty wrthls pst.

Reply to
Nappy

Rule of thumb with Keil. Write the sub in C and look at the asm. ( Or at least the data access parts) if the var is define in C you may get that Underscore thing (_burnAddress ???)

Try it with an int first I THINK Keil calls internal libs for long, but does ints in place. That varies by compiler version I guess.

Reply to
Neil Kurzman

parts)

???)

does

Thank you Neil.

Reply to
Nappy

which

the

char

address

I

Check if Keil realy use big endian for storing long variables. May be yo need to exchnge MSB with LSB.

Reply to
bis

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