Forums

BDM and CAN BUS interaction

Started by Longworth, Kevin December 9, 2002

When I use the Isystem BDM for the Star12 DP256, and using some third party
CAN software, I get a TRUE returned from a function which tells if the bus
is in limp home mode. When this happens it is OK to disable the CAN
tranciever, which I do by pulling the ENE and STBY pins low. Without the
BDM, of course I can't debug, but the ENE and STBY never go low, under the
excact same bus circumstances from the tester. This is indicating the limp
home routine returns FALSE even when the bus should be in limp home state.
The BDM doesn't connect directly to any CAN lines. We are using CAN0 and
this is an 80 pin device. I verifed the program in flash is the same as the
code downloaded to the BDM. Does anyone know how just having the BDM
connected could affect the CAN bus? I hope someone can shed some light on
this, as I have a deadling coming real soon, and don't have a clue as to
what to do next.

- Kevin Longworth



Kevin,

Does the CAN bus operate normally otherwise when the BDM tool is not connected?
If not it may be that your code is writing a '0' to the CANE bit (write once in
normal modes) in the CANCTL1 register, disabling the CAN module. If this is the
case, the code works when the BDM tool is connected because the BDM
tool/software is resetting the part in Special mode and the CANE bit is write
anytime in Special mode. Check out the CAN register initialization sequence.

Regards,
Gordon

"Longworth, Kevin" wrote:

>
> When I use the Isystem BDM for the Star12 DP256, and using some third party
> CAN software, I get a TRUE returned from a function which tells if the bus
> is in limp home mode. When this happens it is OK to disable the CAN
> tranciever, which I do by pulling the ENE and STBY pins low. Without the
> BDM, of course I can't debug, but the ENE and STBY never go low, under the
> excact same bus circumstances from the tester. This is indicating the limp
> home routine returns FALSE even when the bus should be in limp home state.
> The BDM doesn't connect directly to any CAN lines. We are using CAN0 and
> this is an 80 pin device. I verifed the program in flash is the same as the
> code downloaded to the BDM. Does anyone know how just having the BDM
> connected could affect the CAN bus? I hope someone can shed some light on
> this, as I have a deadling coming real soon, and don't have a clue as to
> what to do next.
>
> - Kevin Longworth >
>
> -------------------- >
> ">http://docs.yahoo.com/info/terms/

--
===============================================================
Gordon Doughman Ph: 937-438-6811
Motorola Semiconductor Fax: 937-434-7457
Field Applications Engineer Pager: 800-759-8352 Pin: 1304089
Suite 175
3131 Newmark Drive
Miamisburg, OH 45342

Check out my HC12 book at:
http://www.rtcgroup.com/books/


Yes, the CAN0 bus works normally otherwise.

- Kevin

-----Original Message-----
From: Gordon Doughman [mailto:]
Sent: Monday, December 09, 2002 9:38 AM
To:
Subject: Re: [68HC12] BDM and CAN BUS interaction
Kevin,

Does the CAN bus operate normally otherwise when the BDM tool is not
connected?
If not it may be that your code is writing a '0' to the CANE bit (write once
in
normal modes) in the CANCTL1 register, disabling the CAN module. If this is
the
case, the code works when the BDM tool is connected because the BDM
tool/software is resetting the part in Special mode and the CANE bit is
write
anytime in Special mode. Check out the CAN register initialization sequence.

Regards,
Gordon

"Longworth, Kevin" wrote:

>
> When I use the Isystem BDM for the Star12 DP256, and using some third
party
> CAN software, I get a TRUE returned from a function which tells if the bus
> is in limp home mode. When this happens it is OK to disable the CAN
> tranciever, which I do by pulling the ENE and STBY pins low. Without the
> BDM, of course I can't debug, but the ENE and STBY never go low, under
the
> excact same bus circumstances from the tester. This is indicating the limp
> home routine returns FALSE even when the bus should be in limp home state.
> The BDM doesn't connect directly to any CAN lines. We are using CAN0 and
> this is an 80 pin device. I verifed the program in flash is the same as
the
> code downloaded to the BDM. Does anyone know how just having the BDM
> connected could affect the CAN bus? I hope someone can shed some light on
> this, as I have a deadling coming real soon, and don't have a clue as to
> what to do next.
>
> - Kevin Longworth >
>
> --------------------
> <http://www.motorola.com/mcu > ">http://docs.yahoo.com/info/terms/
<http://docs.yahoo.com/info/terms/>

--
===============================================================
Gordon Doughman Ph: 937-438-6811
Motorola Semiconductor Fax: 937-434-7457
Field Applications Engineer Pager: 800-759-8352 Pin: 1304089
Suite 175
3131 Newmark Drive
Miamisburg, OH 45342

Check out my HC12 book at:
http://www.rtcgroup.com/books/ <http://www.rtcgroup.com/books/
<http://rd.yahoo.com/M$0188.2647639.4038785.2225243/D=egroupweb/S065542
05:HM/A21406/R=0/*http://www.e-dealsdaily.com/soundbug/>

<http://us.adserver.yahoo.com/l?M$0188.2647639.4038785.2225243/D=egroupmai
l/S=:HM/A21406/rand4221514>

--------------------
<http://www.motorola.com/mcu ">http://docs.yahoo.com/info/terms/> .




Update, the problem was a missing common ground from the test pc with
Vector's cancardx and the DUT. I put earthgournd on the neg terminal of the
DUT power supply and the problem went away. I didn't investigate further,
but I suspect the BDM ground was connected to earth ground and allowed it to
work properly

- Kevin
-----Original Message-----
From: Longworth, Kevin
Sent: Monday, December 09, 2002 1:35 PM
To:
Subject: RE: [68HC12] BDM and CAN BUS interaction Yes, the CAN0 bus works normally otherwise.

- Kevin

-----Original Message-----
From: Gordon Doughman [mailto:]
Sent: Monday, December 09, 2002 9:38 AM
To:
Subject: Re: [68HC12] BDM and CAN BUS interaction
Kevin,

Does the CAN bus operate normally otherwise when the BDM tool is not
connected?
If not it may be that your code is writing a '0' to the CANE bit (write once
in
normal modes) in the CANCTL1 register, disabling the CAN module. If this is
the
case, the code works when the BDM tool is connected because the BDM
tool/software is resetting the part in Special mode and the CANE bit is
write
anytime in Special mode. Check out the CAN register initialization sequence.

Regards,
Gordon

"Longworth, Kevin" wrote:

>
> When I use the Isystem BDM for the Star12 DP256, and using some third
party
> CAN software, I get a TRUE returned from a function which tells if the bus
> is in limp home mode. When this happens it is OK to disable the CAN
> tranciever, which I do by pulling the ENE and STBY pins low. Without the
> BDM, of course I can't debug, but the ENE and STBY never go low, under
the
> excact same bus circumstances from the tester. This is indicating the limp
> home routine returns FALSE even when the bus should be in limp home state.
> The BDM doesn't connect directly to any CAN lines. We are using CAN0 and
> this is an 80 pin device. I verifed the program in flash is the same as
the
> code downloaded to the BDM. Does anyone know how just having the BDM
> connected could affect the CAN bus? I hope someone can shed some light on
> this, as I have a deadling coming real soon, and don't have a clue as to
> what to do next.
>
> - Kevin Longworth >
>
> --------------------
> <http://www.motorola.com/mcu>
<http://www.motorola.com/mcu <http://www.motorola.com/mcu> >
>
>
> ">http://docs.yahoo.com/info/terms/
<http://docs.yahoo.com/info/terms/>
<http://docs.yahoo.com/info/terms/ <http://docs.yahoo.com/info/terms/> >

--
===============================================================
Gordon Doughman Ph: 937-438-6811
Motorola Semiconductor Fax: 937-434-7457
Field Applications Engineer Pager: 800-759-8352 Pin: 1304089
Suite 175
3131 Newmark Drive
Miamisburg, OH 45342

Check out my HC12 book at:
http://www.rtcgroup.com/books/ <http://www.rtcgroup.com/books/>
<http://www.rtcgroup.com/books/ <http://www.rtcgroup.com/books/>
<http://rd.yahoo.com/M$0188.2647639.4038785.2225243/D=egroupweb/S065542
<http://rd.yahoo.com/M$0188.2647639.4038785.2225243/D=egroupweb/S065542
>
05:HM/A21406/R=0/*http://www.e-dealsdaily.com/soundbug/
<http://www.e-dealsdaily.com/soundbug/> >

<http://us.adserver.yahoo.com/l?M$0188.2647639.4038785.2225243/D=egroupmai
<http://us.adserver.yahoo.com/l?M$0188.2647639.4038785.2225243/D=egroupmai
>
l/S=:HM/A21406/rand4221514>

--------------------
<http://www.motorola.com/mcu>
<http://www.motorola.com/mcu <http://www.motorola.com/mcu> ">http://docs.yahoo.com/info/terms/ <http://docs.yahoo.com/info/terms/> > .

<http://rd.yahoo.com/M$0188.2647639.4038785.2225243/D=egroupweb/S065542
05:HM/A21406/R=0/*http://www.e-dealsdaily.com/soundbug/>

<http://us.adserver.yahoo.com/l?M$0188.2647639.4038785.2225243/D=egroupmai
l/S=:HM/A21406/randf3640077>

--------------------
<http://www.motorola.com/mcu ">http://docs.yahoo.com/info/terms/> .