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Discussion Groups | M68HC11 | Indexed Addressing

Technical discussions about Freescale Microcontrollers: M68HC11. (Freescale Semiconductor is a Subsidiary of Motorola).

Indexed Addressing - nimish_sudan - Nov 1 18:31:00 2004


Hey guys, new to the group. Just a quick question.
I have the following code:

BEG EQU $1000 ;Start of registers
PORTD EQU 8 ;Adderss of Port D

LDY #BEG
BSET PORTD,Y $18
END

This code just sets the bits at address $1008. My question is:
Instead of using EQU to define PORTD, can I use RMB and make PORTD
variable? The reason I want to make it variable is not for PORTD,
but for something else that I am doing. (This was just the simplest
and probably a very common example of indexed addressing). So my
question is: Is there a way to make the mask a variable when using
indexed addressing mode? It doesn't have to be done using RMB. My
idea was to store the mask at some memory address and then LDAA with
that value and then use BSET A,Y. This doesn't work, but I was
hoping you geniouses could figure it out from there.. :)
Thanks!






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Re: Indexed Addressing - Tony Papadimitriou - Nov 2 10:22:00 2004

----- Original Message -----
From: "nimish_sudan" <>
To: < > question is: Is there a way to make the mask a variable when using
> indexed addressing mode?

Example usage:
...
LDA #$18 ;mask
LDX #$1008 ;address
BSR BSET
...
LDA VAR_MASK ;mask (variable)
LDX VAR_ADDR ;address (variable)
BSR BCLR
...

;---------------------------------------------------
; Purpose: Variable mask BSET
; Input : A = mask
; : X = address

BSET pshy
psha
tsy ;Y -> stacked mask

lda ,x ;get value to update
ora ,y
sta ,x

pula ;restore registers
puly
rts

;---------------------------------------------------
; Purpose: Variable mask BCLR
; Input : A = mask
; : X = address

BCLR pshy
psha
tsy ;Y -> stacked mask

lda ,x ;get value to update
com ,y ;invert mask for ANDing
anda ,y ;clear the user mask bits
com ,y ;restore mask
sta ,x

pula ;restore registers
puly
rts
(If that was homework, let me know how I scored!)




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Re: Re: Indexed Addressing - Author Unknown - Nov 2 16:07:00 2004

You can also place self modifying ?*&%@# code in ram which yields faster code but doccumentation is important.

Regards
Dave > From: "Tony Papadimitriou" <>
> Date: 2004/11/02 Tue AM 10:22:02 EST
> To: <>
> Subject: Re: [m68HC11] Indexed Addressing > ----- Original Message -----
> From: "nimish_sudan" <>
> To: < > > question is: Is there a way to make the mask a variable when using
> > indexed addressing mode?
>
> Example usage:
> ...
> LDA #$18 ;mask
> LDX #$1008 ;address
> BSR BSET
> ...
> LDA VAR_MASK ;mask (variable)
> LDX VAR_ADDR ;address (variable)
> BSR BCLR
> ...
>
> ;---------------------------------------------------
> ; Purpose: Variable mask BSET
> ; Input : A = mask
> ; : X = address
>
> BSET pshy
> psha
> tsy ;Y -> stacked mask
>
> lda ,x ;get value to update
> ora ,y
> sta ,x
>
> pula ;restore registers
> puly
> rts
>
> ;---------------------------------------------------
> ; Purpose: Variable mask BCLR
> ; Input : A = mask
> ; : X = address
>
> BCLR pshy
> psha
> tsy ;Y -> stacked mask
>
> lda ,x ;get value to update
> com ,y ;invert mask for ANDing
> anda ,y ;clear the user mask bits
> com ,y ;restore mask
> sta ,x
>
> pula ;restore registers
> puly
> rts >
> (If that was homework, let me know how I scored!) > Yahoo! Groups Links





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Re: Indexed Addressing - bart homerson - Nov 3 16:27:00 2004

Hmm. Well, from what I can see here, why not do this? By the way, I use the X register becuase it is faster, but if you are using the X register for something else, then simply change ldx to ldy and then change the X to a Y in the Bset instruction.

PORTD EQU $1008
SomeVar RMB 1 'this is the varible that your value will rest in

ldx $1000
bset PORTD,X #SomeVar
END

So what I think you are trying to accomplish, is to be able to change the value in a variable. Simply put whatever value you want inside "SomeVar" and call this sub to set PORTD according to the Value of "SomeVar". Hope this helps...

LF nimish_sudan <> wrote:

Hey guys, new to the group. Just a quick question.
I have the following code:

BEG EQU $1000 ;Start of registers
PORTD EQU 8 ;Adderss of Port D

LDY #BEG
BSET PORTD,Y $18
END

This code just sets the bits at address $1008. My question is:
Instead of using EQU to define PORTD, can I use RMB and make PORTD
variable? The reason I want to make it variable is not for PORTD,
but for something else that I am doing. (This was just the simplest
and probably a very common example of indexed addressing). So my
question is: Is there a way to make the mask a variable when using
indexed addressing mode? It doesn't have to be done using RMB. My
idea was to store the mask at some memory address and then LDAA with
that value and then use BSET A,Y. This doesn't work, but I was
hoping you geniouses could figure it out from there.. :)
Thanks!

Yahoo! Groups Sponsor
Get unlimited calls to

U.S./Canada ---------------------------------
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To
---------------------------------





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Re: Indexed Addressing - nimish_sudan - Nov 3 20:06:00 2004


Thanks for the quickl reply guys!! I really appreciate it. Well,
this is not homework, but you WILL be getting credit in my project
for helping me on the code. The only thing I don't understand about
the code below is

> LDA VAR_MASK ;mask (variable)
> LDX VAR_ADDR ;address (variable)
> BSR BCLR

Where and when do I assign these? And to what value? This might be
simple stuff, but if you wouldn't mind a little more detail, I would
really appreciate it. Also, I thought variable names, routines
names, etc. couldn't be named after keywords such as BSET and BCLR?
Thanks again for the effort so far!
--- In , "Tony Papadimitriou" <tonyp@m...>
wrote:
> ----- Original Message -----
> From: "nimish_sudan" <nimish_sudan@y...>
> To: < > > question is: Is there a way to make the mask a variable when
using
> > indexed addressing mode?
>
> Example usage:
> ...
> LDA #$18 ;mask
> LDX #$1008 ;address
> BSR BSET
> ...
> LDA VAR_MASK ;mask (variable)
> LDX VAR_ADDR ;address (variable)
> BSR BCLR
> ...
>
> ;---------------------------------------------------
> ; Purpose: Variable mask BSET
> ; Input : A = mask
> ; : X = address
>
> BSET pshy
> psha
> tsy ;Y -> stacked mask
>
> lda ,x ;get value to update
> ora ,y
> sta ,x
>
> pula ;restore registers
> puly
> rts
>
> ;---------------------------------------------------
> ; Purpose: Variable mask BCLR
> ; Input : A = mask
> ; : X = address
>
> BCLR pshy
> psha
> tsy ;Y -> stacked mask
>
> lda ,x ;get value to update
> com ,y ;invert mask for ANDing
> anda ,y ;clear the user mask bits
> com ,y ;restore mask
> sta ,x
>
> pula ;restore registers
> puly
> rts
>
> tonyp@a...
>
> (If that was homework, let me know how I scored!)






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Re: Indexed Addressing - nimish_sudan - Nov 3 23:15:00 2004


You know what, sorry for the earlier post, but I think I understand
your post. Correct me if i'm wrong: You're giving me 2 different
ways to do it, first by have pre-set mask and variable and the
second by using variables that can be modified at any time. So far
so good? Then for each function (oh and I checked, I guess you CAN
use BSET and BCLR as function names) you perform the appropriate
tasks (either ORA or ANDA) to BSET or BCLR. If this is correct
(which I hope it is, because otherwise I'm totally lost), then I
have one last question for you.
Would the process be similar if I wanted to LDAA SOMEVAR,Y?
I am forming a constant character as follows:
MESSAGE1 FCC 'Some Message'
FCB 0
...
LDY #MESSAGE
JSR PRINT
...
PRINT PSHA
PR01 LDAA 0,Y
BEQ PRDONE
JSR LCDOUT
BRA PR01
PRDONE PULA
RTS

And instead of loading a predefined character each time (with LDAA
0,Y), can I use SOMEVAR and vary the number whenever I want (LDAA
SOMEVAR,Y)?
This is really the question I was trying to get at when I first
posted the entire question. But I couldn't figure out how to explain
what I was trying to do.
Thanks again for the quick reply guys. Would greatly appreciate any
more help you guys can provide! I'll try it myself right now, but if
you guys can give me some clues that would be great! :) --- In , "Tony Papadimitriou" <tonyp@m...>
wrote:
> ----- Original Message -----
> From: "nimish_sudan" <nimish_sudan@y...>
> To: < > > question is: Is there a way to make the mask a variable when
using
> > indexed addressing mode?
>
> Example usage:
> ...
> LDA #$18 ;mask
> LDX #$1008 ;address
> BSR BSET
> ...
> LDA VAR_MASK ;mask (variable)
> LDX VAR_ADDR ;address (variable)
> BSR BCLR
> ...
>
> ;---------------------------------------------------
> ; Purpose: Variable mask BSET
> ; Input : A = mask
> ; : X = address
>
> BSET pshy
> psha
> tsy ;Y -> stacked mask
>
> lda ,x ;get value to update
> ora ,y
> sta ,x
>
> pula ;restore registers
> puly
> rts
>
> ;---------------------------------------------------
> ; Purpose: Variable mask BCLR
> ; Input : A = mask
> ; : X = address
>
> BCLR pshy
> psha
> tsy ;Y -> stacked mask
>
> lda ,x ;get value to update
> com ,y ;invert mask for ANDing
> anda ,y ;clear the user mask bits
> com ,y ;restore mask
> sta ,x
>
> pula ;restore registers
> puly
> rts
>
> tonyp@a...
>
> (If that was homework, let me know how I scored!)






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Re: Re: Indexed Addressing - Tony Papadimitriou - Nov 4 3:40:00 2004

----- Original Message -----
From: "nimish_sudan" <>
To: < > Would the process be similar if I wanted to LDAA SOMEVAR,Y?

> And instead of loading a predefined character each time (with LDAA
> 0,Y), can I use SOMEVAR and vary the number whenever I want (LDAA
> SOMEVAR,Y)?

There is no such addressing mode in the HC11.

But you can use the B register instead of SOMEVAR and do and addition with
the X
or Y register using ABX or ABY.

For example:

PSHX ;save X if you don't want it
destroyed
PSHB
LDB SOMEVAR
ABX
LDA ,X
PULB
PULX ;restore X

The above will load A with the value at address (X + the 8-bit contents of
SOMEVAR)






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Re: Indexed Addressing - Paul B. Webster - Nov 4 5:17:00 2004

On Thu, 2004-11-04 at 08:27, bart homerson wrote:
> SomeVar RMB 1 'this is the varible that your value will rest in
> ...
> bset PORTD,X #SomeVar

I may be a bit rusty, but that does *not* look right to me!

--
Cheers,
Paul B.




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Re: Indexed Addressing - Scott Grodevant - Nov 4 8:48:00 2004

Hi all,

In this instance, #SomeVar evaluates to the address of SomeVar, not it's value (content). So Paul is right on the money. I doubt that's what the original author had in mind.

Scott "Paul B. Webster" <> wrote:
On Thu, 2004-11-04 at 08:27, bart homerson wrote:
> SomeVar RMB 1 'this is the varible that your value will rest in
> ...
> bset PORTD,X #SomeVar

I may be a bit rusty, but that does *not* look right to me!

--
Cheers,
Paul B. Yahoo! Groups SponsorADVERTISEMENT ---------------------------------
Yahoo! Groups Links

To
---------------------------------





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Re: Indexed Addressing - Mark Schultz - Nov 4 10:34:00 2004


--- In , "nimish_sudan" <nimish_sudan@y...>
wrote:
> MESSAGE1 FCC 'Some Message'
> FCB 0
> ...
> LDY #MESSAGE
> JSR PRINT
> ...
> PRINT PSHA
> PR01 LDAA 0,Y
> BEQ PRDONE
> JSR LCDOUT
> BRA PR01
> PRDONE PULA
> RTS

What you are doing above will work just fine - almost. You forgot to
increment the index register (Y) in the above code. As written, your
PRINT routine will output the first letter of your string ('S')
forever. Add a 'INY' instruction between the BEQ PRDONE and JSR
LCDOUT.

You may, of course, use the X register instead of Y if you prefer.
Since I tend to use the X register for I/O register access, I usually
write routines like the one above to use Y, as you have done.

-- Mark



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Re: Indexed Addressing - Mark Schultz - Nov 4 10:44:00 2004


--- In , "nimish_sudan" <nimish_sudan@y...>
wrote:
>
> Thanks for the quickl reply guys!! I really appreciate it. Well,
> this is not homework, but you WILL be getting credit in my project
> for helping me on the code. The only thing I don't understand about
> the code below is
>
> > LDA VAR_MASK ;mask (variable)
> > LDX VAR_ADDR ;address (variable)
> > BSR BCLR
>
> Where and when do I assign these? And to what value? This might be
> simple stuff, but if you wouldn't mind a little more detail, I
> would really appreciate it. Also, I thought variable names,
> routines names, etc. couldn't be named after keywords such as BSET
> and BCLR? Thanks again for the effort so far!

The above example simply illustrates that you can use a VARIABLE
value (e.g. something stored in RAM) as parameters to the BSET/BCLR
subroutines. You could just as easily load A and X with constant
values (e.g. LDAA #$10; LDX #$1008) instead of loading A and X from
RAM variables. It's up to you. 'VAR_MASK' and 'VAR_ADDR' were not
explicitly declared in the example you were given.

I don't remember if Mot's AS11 assembler (or Tony P's ASM11) allow
label names to be the same as instruction mnemonics. My personal
practice is to avoid using label names that are the same as
instruction or register names - not only does this avoid a (possible)
assembler error, it minimizes confusion. I probably would have named
the subroutines 'BSETV' and 'BCLRV' (for 'Bit Set Variable' and 'Bit
Clear Variable', respectively).

-- Mark



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Re: Indexed Addressing - bart homerson - Nov 5 10:07:00 2004

Hmm. What part doesn't look right?
This is indexed addressing, by using the BSET instruction you want to set the appropriate bits that correspond to the mask, which is SomeVar. Since X is loaded with $1000 then we can assume that PORTD is $08, and so PORTD is manipulated by the value resting in SomeVar. Perhaps it was the lack of definition for PORTD that threw you off. Sorry, I was just trying to keep it simple for the guy.

LF

"Paul B. Webster" <> wrote:
On Thu, 2004-11-04 at 08:27, bart homerson wrote:
> SomeVar RMB 1 'this is the varible that your value will rest in
> ...
> bset PORTD,X #SomeVar

I may be a bit rusty, but that does *not* look right to me!

--
Cheers,
Paul B. Yahoo! Groups SponsorADVERTISEMENT ---------------------------------
Yahoo! Groups Links

To
---------------------------------




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Re: Indexed Addressing - bart homerson - Nov 5 10:10:00 2004

I am sorry, you have this all wrong. IF I left out the "#" in "#SomeVar", then I would be wanting the address corresponding to the value in SomeVar. In fact, the "#" means the literal value of the variable and NOT the address of the value within the varible.

LF

Scott Grodevant <> wrote:
Hi all,

In this instance, #SomeVar evaluates to the address of SomeVar, not it's value (content). So Paul is right on the money. I doubt that's what the original author had in mind.

Scott "Paul B. Webster" <> wrote:
On Thu, 2004-11-04 at 08:27, bart homerson wrote:
> SomeVar RMB 1 'this is the varible that your value will rest in
> ...
> bset PORTD,X #SomeVar

I may be a bit rusty, but that does *not* look right to me!

--
Cheers,
Paul B. Yahoo! Groups SponsorADVERTISEMENT ---------------------------------
Yahoo! Groups Links

To
---------------------------------
Yahoo! Groups SponsorADVERTISEMENT ---------------------------------
Yahoo! Groups Links

To
---------------------------------





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Re: Indexed Addressing - Tony Papadimitriou - Nov 5 10:14:00 2004

----- Original Message -----
From: "bart homerson" <>
To: <>

> Hmm. What part doesn't look right?

>>SomeVar RMB 1 'this is the varible that your value will rest in
>>...
>>bset PORTD,X #SomeVar

*That* doesn't look right! #SomeVar gets the value of the lowbyte (depending on
assembler) of the address of SomeVar and uses it as mask! I don't think anybody
intentionally would do that!

> LF
> "Paul B. Webster" <> wrote:
> On Thu, 2004-11-04 at 08:27, bart homerson wrote:
> > SomeVar RMB 1 'this is the varible that your value will rest in
> > ...
> > bset PORTD,X #SomeVar
>
> I may be a bit rusty, but that does *not* look right to me!

> Paul B.




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Re: Indexed Addressing - Tony Papadimitriou - Nov 5 10:18:00 2004

----- Original Message -----
From: "bart homerson" <>
To: < > I am sorry, you have this all wrong. IF I left out the "#" in "#SomeVar",
then I would be wanting the address corresponding to the value in SomeVar. In
fact, the "#" means the literal value of the variable and NOT the address of the
value within the varible.

For BSET/BCLR/BRSET/BRCLR instructions, the # is optional and does NOT affect
the instruction at all!

> LF





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Re: Indexed Addressing - bart homerson - Nov 5 10:31:00 2004

NONONO, not the ADDRESS, but the VALUE, or NUMBER, That is in "SomeVar". I use the AS11 assembler, and I have used this very same code snippet in a program that has been working for over two years now. YES, the "#" is necessary, if it were not there then the code would look at the ADDRESS of "SomeVar" and NOT the VALUE in "SomeVar".

LF

Tony Papadimitriou <> wrote:

----- Original Message -----
From: "bart homerson"
To:

> Hmm. What part doesn't look right?

>>SomeVar RMB 1 'this is the varible that your value will rest in
>>...
>>bset PORTD,X #SomeVar

*That* doesn't look right! #SomeVar gets the value of the lowbyte (depending on
assembler) of the address of SomeVar and uses it as mask! I don't think anybody
intentionally would do that!

> LF
> "Paul B. Webster"
wrote:
> On Thu, 2004-11-04 at 08:27, bart homerson wrote:
> > SomeVar RMB 1 'this is the varible that your value will rest in
> > ...
> > bset PORTD,X #SomeVar
>
> I may be a bit rusty, but that does *not* look right to me!

> Paul B. Yahoo! Groups Links
---------------------------------




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Re: Indexed Addressing - Tony Papadimitriou - Nov 5 10:34:00 2004

----- Original Message -----
From: "bart homerson" <>
To: < > NONONO, not the ADDRESS, but the VALUE, or NUMBER, That is in "SomeVar". I
use the AS11 assembler, and I have used this very same code snippet in a program
that has been working for over two years now. YES, the "#" is necessary, if it
were not there then the code would look at the ADDRESS of "SomeVar" and NOT the
VALUE in "SomeVar".

Sorry to break this news to you but your program has been working by pure
chance!

> LF






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Re: Indexed Addressing - Homer Simpson - Nov 5 10:40:00 2004


LOL, Incorrect.

Perhaps I should have included something like this in my initial code
snippet:

ldaa #%01010101
staa SomeVar

It does work, I swear! lol

take care.

LF --- In , "Tony Papadimitriou" <tonyp@m...>
wrote:
> ----- Original Message -----
> From: "bart homerson" <odddooo1@y...>
> To: < > > NONONO, not the ADDRESS, but the VALUE, or NUMBER, That is
in "SomeVar". I
> use the AS11 assembler, and I have used this very same code snippet
in a program
> that has been working for over two years now. YES, the "#" is
necessary, if it
> were not there then the code would look at the ADDRESS of "SomeVar"
and NOT the
> VALUE in "SomeVar".
>
> Sorry to break this news to you but your program has been working
by pure
> chance!
>
> > LF
>
> tonyp@a...





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Re: Indexed Addressing - Scott Grodevant - Nov 5 10:52:00 2004

Hi all and LF,

I suggest you look at the object code that is generated and confirm what your instruction actually does. When in doubt this method 100% confirms what will happen.

The HC11 has no memory to memory bit manipulation functions so it cannot set the bits of one memory location based on an OR mask contained in another (unless you count the memory from which the instructions are running, e.g. self-modifying code).

I agree with Tony's comment (a different email on the same thread) about some assemblers not needing the #. Scott bart homerson <> wrote:
I am sorry, you have this all wrong. IF I left out the "#" in "#SomeVar", then I would be wanting the address corresponding to the value in SomeVar. In fact, the "#" means the literal value of the variable and NOT the address of the value within the varible.

LF

Scott Grodevant <> wrote:
Hi all,

In this instance, #SomeVar evaluates to the address of SomeVar, not it's value (content). So Paul is right on the money. I doubt that's what the original author had in mind.

Scott "Paul B. Webster" <> wrote:
On Thu, 2004-11-04 at 08:27, bart homerson wrote:
> SomeVar RMB 1 'this is the varible that your value will rest in
> ...
> bset PORTD,X #SomeVar

I may be a bit rusty, but that does *not* look right to me!

--
Cheers,
Paul B. Yahoo! Groups SponsorADVERTISEMENT ---------------------------------
Yahoo! Groups Links

To
---------------------------------
Yahoo! Groups SponsorADVERTISEMENT ---------------------------------
Yahoo! Groups Links

To
---------------------------------
Yahoo! Groups SponsorADVERTISEMENT ---------------------------------
Yahoo! Groups Links

To
---------------------------------




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Re: Indexed Addressing - Scott Grodevant - Nov 5 10:59:00 2004

Hi all and Tony,

Yes, Tony's right. The the address of SomeVar is ORed with the content of PORTD+X and placed back in PORTD+X. Most assemblers would generate a warning if the address of SomeVar is larger than 255 ($FF).

Scott Tony Papadimitriou <> wrote:

----- Original Message -----
From: "bart homerson"
To:

> Hmm. What part doesn't look right?

>>SomeVar RMB 1 'this is the varible that your value will rest in
>>...
>>bset PORTD,X #SomeVar

*That* doesn't look right! #SomeVar gets the value of the lowbyte (depending on
assembler) of the address of SomeVar and uses it as mask! I don't think anybody
intentionally would do that!

> LF
> "Paul B. Webster"
wrote:
> On Thu, 2004-11-04 at 08:27, bart homerson wrote:
> > SomeVar RMB 1 'this is the varible that your value will rest in
> > ...
> > bset PORTD,X #SomeVar
>
> I may be a bit rusty, but that does *not* look right to me!

> Paul B. Yahoo! Groups Links
---------------------------------




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Re: Re: Indexed Addressing - Tony Papadimitriou - Nov 5 11:02:00 2004

----- Original Message -----
From: "Homer Simpson" <>
To: <>

>Perhaps I should have included something like this in my initial code snippet:
>
>ldaa #%01010101
>staa SomeVar
>
> It does work, I swear! lol

Oh, you must be right then! Would you be so kind to please inform the list what
company(-ies) you've been writing programs for so we can protect ourselves from
their fine products.

LOL! (There are limits to how much I can take in a single day, please stop!)

> LF






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Re: Indexed Addressing - Homer Simpson - Nov 5 12:53:00 2004


LMAO! Ok, Ok, I stand corrected. I went back and took a look at my
code, remember this was two years ago when I wrote this, and I
realized that I *wanted* to do what I have been protesting here, but
it would not work. I guess it was implanted in my brain that it did
work, but now I realize how ridiculous I have been sounding, and so I
will go crawl in a corner now. Sorry for the misinformation, but I
am glad I learned something from it. Thank you all.

LF --- In , "Tony Papadimitriou" <tonyp@m...>
wrote:
> ----- Original Message -----
> From: "Homer Simpson" <odddooo1@y...>
> To: <>
>
> >Perhaps I should have included something like this in my initial
code snippet:
> >
> >ldaa #%01010101
> >staa SomeVar
> >
> > It does work, I swear! lol
>
> Oh, you must be right then! Would you be so kind to please inform
the list what
> company(-ies) you've been writing programs for so we can protect
ourselves from
> their fine products.
>
> LOL! (There are limits to how much I can take in a single day,
please stop!)
>
> > LF
>
> tonyp@a...





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Re: Indexed Addressing - nimish_sudan - Nov 5 20:09:00 2004


Wow Tony, it works! Thanks for your help, and thanks for everyone
else as well for their ideas. It doesn't matter who's right or
wrong, as long as we all learn from our mistakes.
Thanks again!

--- In , "Tony Papadimitriou" <tonyp@m...>
wrote:
> ----- Original Message -----
> From: "nimish_sudan" <nimish_sudan@y...>
> To: < > > Would the process be similar if I wanted to LDAA SOMEVAR,Y?
>
> > And instead of loading a predefined character each time (with
LDAA
> > 0,Y), can I use SOMEVAR and vary the number whenever I want (LDAA
> > SOMEVAR,Y)?
>
> There is no such addressing mode in the HC11.
>
> But you can use the B register instead of SOMEVAR and do and
addition with
> the X
> or Y register using ABX or ABY.
>
> For example:
>
> PSHX ;save X if you don't
want it
> destroyed
> PSHB
> LDB SOMEVAR
> ABX
> LDA ,X
> PULB
> PULX ;restore X
>
> The above will load A with the value at address (X + the 8-bit
contents of
> SOMEVAR)
>
> tonyp@a...





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