Another QMAC question.....

[prime]

Ok,

So I'm trying to port the released QLSD source for use in my own hardware implementation. This will be on a standard expansion card and so i will need to put the I/O registers at a specified offset from the beginning of the ROM and **NOT** an absolute address.

I just can't figure out how to do this in QMAC

I know i will need something like :

Code: Select all

 REGBASE	equ	$3ff0

	lea	REGBASE(PC),a5
	

this however generates the error :

Code: Select all

  86 01 00000020 4BFA3FCE     	lea	IFBASE(PC),a5
                                   |
****** ERROR 31 -- line   86 -    0 - wrong relocation for PC-relative address

Any idea what I can do to fix this ?

Cheers.

Phill.

[tofro]

Phill,

try an indexed register, somewhat like that:

Code: Select all

ROMSTART:              dc.l $4afb0001
CODESTART:             lea ROMSTART(PC),a0
                       move.l     #register_offset,d0
                       lea 0(a0,d0.w),a0

This should work. PC-relative addressing doesn't like absolute offsets that are directly equated (I pretty much doubt that even if it had worked you'd be ending up at the correct address - I guess you put in the absolute offset of the registers from the beginning instead of the the difference between the PC and the register...). It want's to see these in your code and calculate on its own....

Tobias

[ql_freak]

Ok,

So I'm trying to port the released QLSD source for use in my own hardware implementation. This will be on a standard expansion card and so i will need to put the I/O registers at a specified offset from the beginning of the ROM and **NOT** an absolute address.

I just can't figure out how to do this in QMAC :(

I know i will need something like :

Code: Select all

 REGBASE	equ	$3ff0

	lea	REGBASE(PC),a5
	

this however generates the error :

Code: Select all

  86 01 00000020 4BFA3FCE     	lea	IFBASE(PC),a5
                                   |
****** ERROR 31 -- line   86 -    0 - wrong relocation for PC-relative address

Any idea what I can do to fix this ?

You load relative to the PC (program counter) with LEA (load effective address?) an absolute address(?). Relative addressing on the 68k is only -32768 to +32767 (it is not a real 32-bit processor). So if your program is loaded in the TPA, this relative addressing is too large?

Don't know, if this is correct (I haven't do any programming for 68k for long times) - so the assembler (the 68k-processor) can't relocate (do) this (physically not cabable).

[ppe]

Ok,

I know i will need something like :

Code: Select all

 REGBASE	equ	$3ff0

	lea	REGBASE(PC),a5
	

Any idea what I can do to fix this ?

Cheers.

Phill.

Hi Phill,

I think you need to leave out the "(pc)" bit in assembler source and just specify the offset, i.e, go for

Code: Select all

        lea    REGBASE,a5

Kind regards,
Petri

[ql_freak]

I think you need to leave out the "(pc)" bit in assembler source and just specify the offset, i.e, go for

Code: Select all

        lea    REGBASE,a5

I think you are right. The assembler calculates the distance from the PC to the address - programmers are lazy and this saves 4 characters typing ;-)

[prime]

Just as a quick update I fixed it by defining a symbol ROMSTART at the beginning of the ROM then doing :

Code: Select all

	GENIF 	IS_ROMREL = 1
	lea     ROMSTART(PC),a5		; point to base of ROM
	ENDGEN
	
	GENIF 	IS_ROMREL = 0
	move.l	#IF_BASE,a5		; a5=Pointer to QLROMEXT control registers
	ENDGEN

And then defining all the offsets for the IO relative to the start of the ROM if ROMREL=1, and relative to IF_BASE if not.

Cheers.

Phill.