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Discussion Groups | M68HC11 | Reset program

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

Reset program - nimish_sudan - Nov 10 1:53:00 2004


Hey guys, another question here. This one might be kind of tricky
because I've looked around for the answer but haven't been
successful. I'd like to know if there is a way to reset an assembly
program at run-time using assembly code? By reset I mean essentially
have to go to the ORG line where it all started initially. I'm not
sure if this is dependent on what type of board is being used, but I
would assume that the code would be similar, if not same, since its
the same language. Thanks for any ideas on this one! :)






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Re: Reset program - Tony Papadimitriou - Nov 10 4:51:00 2004

----- Original Message -----
From: "nimish_sudan" <>
To: < > Hey guys, another question here. This one might be kind of tricky
> because I've looked around for the answer but haven't been
> successful. I'd like to know if there is a way to reset an assembly
> program at run-time using assembly code? By reset I mean essentially
> have to go to the ORG line where it all started initially. I'm not
> sure if this is dependent on what type of board is being used, but I
> would assume that the code would be similar, if not same, since its
> the same language. Thanks for any ideas on this one! :)

Try this code which uses the Clock Monitor to cause a reset:

sei ;disable interrupts

tpa ;\
anda #$7F ; >enable STOP instruction
tap ;/
ldx #REGS
bset [OPTION,x,#CME. ;stop the clock, forcing a
CMF
Stop stop ;This command causes a CMF
res
bra Stop ;just in case of
XIRQ escaping




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Re: Reset program - nimish_sudan - Nov 10 21:29:00 2004


Thanks for the quick reply Tony! I tried the code, but I was
unsuccessful. Its probably because I am new to assembly and have not
mastered it like you. :) Could you please go into a little detail
and explain how/why you have done what you have done? What are the
values of Option and CME in the following line? And should the
bracket be closed or not?

>bset [OPTION,x,#CME. ;stop the clock,

Thanks again for the quick reply. Much appreciated! --- In , "Tony Papadimitriou" <tonyp@m...>
> Try this code which uses the Clock Monitor to cause a reset:
>
> sei ;disable
interrupts
>
> tpa ;\
> anda #$7F ; >enable STOP
instruction
> tap ;/
> ldx #REGS
> bset [OPTION,x,#CME. ;stop the clock,
forcing a
> CMF
> Stop stop ;This command
causes a CMF
> res
> bra Stop ;just in
case of
> XIRQ escaping > tonyp@a...





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Re: Re: Reset program - Tony Papadimitriou - Nov 11 12:58:00 2004

----- Original Message -----
From: "nimish_sudan" <>
To: < > Thanks for the quick reply Tony! I tried the code, but I was
> unsuccessful. Its probably because I am new to assembly and have not
> mastered it like you. :) Could you please go into a little detail
> and explain how/why you have done what you have done? What are the
> values of Option and CME in the following line? And should the
> bracket be closed or not?

> >bset [OPTION,x,#CME. ;stop the clock,

The symbols REGS, OPTION, and CME. must be defined with EQU somewhere before
this code begins. The "[" syntax is for my ASM11 assembler but even without the
"[" it works OK. All it says, is to use the low byte of the value (which it
does anyway, but will give a warning).

REGS is normally $1000 but it really depends on your hardware (MCU and/or
external memory requiring a move of the registers to another page).
OPTION is $1039 (or REGS+$39) for the E series, and again, it depends on the
particular MCU.
CME. is the bit mask for the CME (Clock Monitor Enable) bit in the OPTION
register. For E series, this is %00001000

The idea with this code is to stop the clock of the MCU and have it reset based
on that condition. The reset is as real as it gets. It's not the same as
simply JMP-ing to the start of your code.

> Thanks again for the quick reply. Much appreciated!






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Re: Reset program - nimish_sudan - Nov 12 13:02:00 2004


Hey Tony,
Thanks for the explanation. Just another quick question. Does
this reset only work when you're running the program from the
EEPROM? Right now I'm NOT using the EEPROM and it just seems to stop
execution (and not restart from the top) where the code is in my
program. Thanks again!

--- In , "Tony Papadimitriou" <tonyp@m...>
wrote:
> ----- Original Message -----
> From: "nimish_sudan" <nimish_sudan@y...>
> To: < > > Thanks for the quick reply Tony! I tried the code, but I was
> > unsuccessful. Its probably because I am new to assembly and have
not
> > mastered it like you. :) Could you please go into a little detail
> > and explain how/why you have done what you have done? What are
the
> > values of Option and CME in the following line? And should the
> > bracket be closed or not?
>
> > >bset [OPTION,x,#CME. ;stop the clock,
>
> The symbols REGS, OPTION, and CME. must be defined with EQU
somewhere before
> this code begins. The "[" syntax is for my ASM11 assembler but
even without the
> "[" it works OK. All it says, is to use the low byte of the value
(which it
> does anyway, but will give a warning).
>
> REGS is normally $1000 but it really depends on your hardware (MCU
and/or
> external memory requiring a move of the registers to another page).
> OPTION is $1039 (or REGS+$39) for the E series, and again, it
depends on the
> particular MCU.
> CME. is the bit mask for the CME (Clock Monitor Enable) bit in the
OPTION
> register. For E series, this is %00001000
>
> The idea with this code is to stop the clock of the MCU and have
it reset based
> on that condition. The reset is as real as it gets. It's not the
same as
> simply JMP-ing to the start of your code.
>
> > Thanks again for the quick reply. Much appreciated!
>
> tonyp@a...





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Re: Re: Reset program - Tony Papadimitriou - Nov 12 14:03:00 2004

----- Original Message -----
From: "nimish_sudan" <>
To: < > Thanks for the explanation. Just another quick question. Does
> this reset only work when you're running the program from the
> EEPROM? Right now I'm NOT using the EEPROM and it just seems to stop
> execution (and not restart from the top) where the code is in my
> program. Thanks again!

Not only for EEPROM, it works regardless!

Maybe you forgot to initialize the CMF vector with the same value as the RESET
vector?






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Re: Reset program - nimish_sudan - Nov 12 17:32:00 2004


Tony,
As before, you're probably right. :) What value should these
vectors be initialized to? This is what I have:

BEG EQU $1000
OPTION EQU 39
CME EQU 8
...
...
SEI
LDX #BEG
BSET OPTION,X #CME
TPA
ANDA #$7F
TAP
NOP
STOPME STOP
BRA STOPME
...

Thank again for the fast response!

--- In , "Tony Papadimitriou" <tonyp@m...>
wrote:
> ----- Original Message -----
> From: "nimish_sudan" <nimish_sudan@y...>
> To: < > > Thanks for the explanation. Just another quick question. Does
> > this reset only work when you're running the program from the
> > EEPROM? Right now I'm NOT using the EEPROM and it just seems to
stop
> > execution (and not restart from the top) where the code is in my
> > program. Thanks again!
>
> Not only for EEPROM, it works regardless!
>
> Maybe you forgot to initialize the CMF vector with the same value
as the RESET
> vector?
>
> tonyp@a...






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Re: Re: Reset program - Tony Papadimitriou - Nov 13 6:47:00 2004

----- Original Message -----
From: "nimish_sudan" <>
To: < > Tony,
> As before, you're probably right. :) What value should these
> vectors be initialized to? This is what I have:

> OPTION EQU 39

Make that a hex value, $39

The CMF vector is the one right before reset (at address $FFFC). You can
initialize it as you do for the reset vector.

Example:

ORG $FFFC
DW Start ;CMF vector
DW Start ;RESET vector

> Thank again for the fast response!





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