Indirect JMP?

[wolf99]

Hi Folks

If I have an address stored in, say DPTR reg, how should I jump to that address?
(Its a long long while since Ive used asm so bear with me!)

Keil throws a syntax error for

LJMP DPTR

and also for

LJMP @DPTR

so.... stuck, guess Im not using LJUMP correctly??
ta

 

[Atheist]

Does this help?
Specifically, this bit:

If you speak about the 51th controller and you need to make a jump to an explicit 16-bit address, you may load this address into DPTR (DPH, DPL), clear your accumulator and use JMP @A+DPTR.
Michael.

 

[wolf99]

Thanks again athiest! I'll give it a try and see what happens.

Had done similar searches in google myself, but obviously not quite got the search query wording right for google to know what I was on about!

 

[wolf99]

Hi so that worked!

MOV A,#0
LJMP @A+DPTR

Yay, Muchos Gracias!

Two other places I need variability is in an ORG instr and a GLOBAL instr. Im not quite sure what this GLOBAL instr does... declares a global variable?

my inline asm is looking like this currently:

	#asm
		GLOBAL _ext1isr
		PSECT vectors,ovrld
		ORG 0x34
		MOV A,#0
		LJMP @A+DPTR
		PSECT text
	#endasm

I want to be able to vary the ORG address and the address used for GLOBAL
something like ORG @B and GLOBAL @DPTR...


EDIT: what I THINK might be happening in the asm code currently is that the two instr.s MOV and LJUMP are placed in code memory at the location 0x34