Experimental Physics and Industrial Control System
All,
This may be of interest to persons that are using the Motorola MVME162.
Jeff
> -----Original Message-----
> From: the vxWorks Users Group Exploder [mailto:[email protected]]
> Sent: Wednesday, August 04, 1999 7:29 AM
> To: [email protected]
> Subject: MVME162 Bug in system clock
>
>
> Submitted-by owner-vxwexplo-process Wed Aug 4 06:28:55 1999
> Submitted-by: David Abbott <[email protected]>
>
>
> Hello vxWorks users,
> I came across what looks to be a very long standing bug in the
> BSP for the Motorola MVME162 single board computer. I thought I would
> pass the info along to anyone who cares.
>
> Our problem ocurred when we were attempting to periodically
> write some status information to a file on an NFS mounted disk. This
> was done every 15 minutes or so. To help keep track of the files,
> we created a filename containing a time/date stamp in its name.
> We noticed that over the course of a day or two the time/date stamps
> were getting further and further out of sync with the UNIX file
> server's time (almost an hour behind over a 24 hour period).
>
> A little investigation into the BSP found that the vxWorks system
> clock is working off one of the tick timers in the MCChip on the MV162.
> These timers rely on prescaling the processor's clock speed down to
> 1 MHz. Hence there is a Prescale Clock Adjust Register on the Chip that
> must be programmed correctly. There is also a CPU Version Register
> that is read only containing information about the the Processor type,
> and the presence of SCSI, ethernet, and VME interface chips.
>
> In syslib.c (sysHwInit), the Version register is checked and the
> Prescale Clock Adjust Register is set for either a 25MHz CPU or a 33 MHz
> CPU (see code snippet):
>
> if (*MCC_VERSION_REG & 0x01) /* check clock speed */
> {
> *MCC_PRESCALE_CLK_ADJ = 256 - 33; /* for 33 MHz board */
> *MCC_PRESCALE = 256 - 33;
> *MCC_BUS_CLK_REG = 33;
> }
> else
> {
> *MCC_PRESCALE_CLK_ADJ = 256 - 25; /* for 25 MHz board */
> *MCC_PRESCALE = 256 - 25;
> *MCC_BUS_CLK_REG = 25;
> }
>
> The problem is that about 4 years ago Motorola introduced the MV162 FX and
> LX series of VME CPUs which run at 25MHz or 32MHz. So if you have a 32MHz
> version of a MV162 the Prescale Clock Adjust Register is set incorrectly
> and the whole vxWorks system clock time base is off by a factor 32/33.
> Hence, when 1 realtime second has passed the vxWorks OS only
> thinks .97 sec
> have passed.
>
> For most of our applications a 3% effect is not an issue, but if folks
> are relying accurate time based applications the fix is easy. Just change
> the above code in sysLib.c replacing the 33 for 32.
>
> A couple of additional notes: First this does not affect the MV167 BSP
> as that board really does run at 33MHz. Also I have noticed that even with
> the latest BSPs distributed with Tornado II and vxWorks 5.4 the
> bug is still
> there.
>
>
>
> ---------------------------------------------------------
> David Abbott Jefferson Lab
> Data Acquisition Group MS 12H
> EMAIL: [email protected] 12000 Jefferson Ave.
> Tel: (757) 269-7190 Newport News, VA 23606
> FAX: (757) 269-5800
> ---------------------------------------------------------
>
>
> **********
>
> This is a user group mailing list for vxWorks related topics
> Mail articles to [email protected] for 'explosion'
> Include the word VxWorks or Tornado to penetrate SPAM filters
> edit off the trailer to avoid bounce filters
> Send subscription requests & comments to [email protected]
>
- Navigate by Date:
- Prev:
FW: GCC generates floating point code on its own for PPC. Jeff Hill
- Next:
RE: Channel Access Gateway software Jeff Hill
- Index:
1994
1995
1996
1997
1998
<1999>
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
- Navigate by Thread:
- Prev:
FW: GCC generates floating point code on its own for PPC. Jeff Hill
- Next:
Array Information Noboru Yamamoto
- Index:
1994
1995
1996
1997
1998
<1999>
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024