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Writing MSCAN CANE bit (56805)

Started by Jan Zizka July 12, 2003
Hi,

in manual there is written following about CANTCL1 register bits
(ch. 8.8.2 of 5680x User's manual):

"These bits are read/write at any time when SFTRES = 1, except CANE.
It is write once in normal modes and any time in special modes when
SFTRES = 1."

But even thou I set SFTRES I can't clear (or set) it after first
write to CANE even thou I set SFTRES = 1. So is it in reality so
that CANE is writable only once?

Jan

PS: here are dumps...

dspd$ dd 0xd80 +0x8
Data memory:
0D80: 0010 0085 0049 0013 0000 0000 0007 0000 dspd$ md 0xd80 +0x1
Data memory:
Current data:
0D80: 0010
Written data:
0D80: 0001 dspd$ dd 0xd80 +0x8
Data memory:
0D80: 0001 0085 0049 0013 0000 0000 0007 0000 dspd$ md 0xd81 +0x5
Data memory:
Current data:
0D81: 0085
Written data:
0D81: 0005 dspd$ dd 0xd80 +0x8
Data memory:
0D80: 0001 0085 0049 0013 0000 0000 0007 0000 dspd$ md 0xd81 +0x0
Data memory:
Current data:
0D81: 0085
Written data:
0D81: 0000 dspd$ dd 0xd80 +0x8
Data memory:
0D80: 0001 0080 0049 0013 0000 0000 0007 0000



Ok! That is what I thought, but what I couldn't understand from the manual
clearly. So why are those 'special modes mentioned at all? If they are not
supposed to be used? Ok I know that many-times this occurs in manuals.

Thanks for all responses!

Jan

On Mon, Jul 14, 2003 at 09:09:16AM -0400, John Breitenbach wrote:
> Jan,
>
> in manual there is written following about CANTCL1 register bits
> (ch. 8.8.2 of 5680x User's manual):
>
> "These bits are read/write at any time when SFTRES = 1, except CANE.
> It is write once in normal modes and any time in special modes when
> SFTRES = 1."
>
> This sentence might have been a little clearer if it was written as three
sentences:
>
> "CANE is write once in normal modes when SFTRES=1. It may be written at any
time in special modes when SFTRES=1. The special modes are undocumented and the
user can/should not ever be running in special mode".
>
> At least that's the way that I read it, and that's the way the bit seems to
function in my code and in yours. Hope that helps.
>
> Best regards,
>
> - John Breitenbach
> - Atlantex Corp.
> - (201) 664-3445
> -
>
> "Quote me as saying I was misquoted" - Groucho Marx