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In lugnet.robotics.rcx.legos, Mark Riley wrote:
> In lugnet.robotics.rcx.legos, Rob Stehlik wrote:
[snip]
>
> As we discussed in email, it appears to be the firmware downloader causing
> the problem. I just tried downloading BrickOS 0.2.6.10 with both NQC 2.5 a1 and
> BricxCC 3.3.6.2 and experienced growling motors. I then downloaded BrickOS
> using firmdl3 and had no problems.
>
> This is the same issue that caused problems with other firmware downloads (such
> as LDCC and LeJOS). For an explanation as to what the problem is, see this
> message:
>
> http://news.lugnet.com/robotics/rcx/java/?n=260
>
> For the morbidly curious, there is a two byte memory gap preceeding the motor
> driver routine (which happens to be the last thing in the memory image), and
> this gap causes the driver to load two bytes lower in memory. Well, the first
> instruction of the motor routine ends up being skipped. This instruction
> happens to zero a register (r6l) that gets written to the motor port, but since
> the instruction isn't being executed, this register inherits whatever
> semi-random value happens to be in r6l at the time.
>
> Mark
Mark,
Thanks for shooting this so quickly.
Kevin
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