Subject:
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Re: Some comments (long) (was: Something else is needed, I think...)
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 6 May 1999 22:51:58 GMT
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Viewed:
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3282 times
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Kekoa Proudfoot wrote in message ...
> Some comments on what Chris Phillips wrote:
>
> - as far as I know, you will not be able to implement floating point in
> byte code, it will be too inefficient (mostly in terms of space)
Do you think it would be possible with improved firmware to support
inline H8 code embedded in a user program? For example, a special byte code
could indicate that the following code should be executed directly by a
subroutine CALL until it decided to RETurn? This might allow compilers to
embed high-performance, efficient library code into a user program instead
of relying on the firmware to implement every feature, or byte code
operations to support every possibility.
> - agreed, current firmware does not support fixed point well, and it is
> because they do not allow 32-bit values
> - yes, you need 32-bit values for usable fixed point in byte code
> - muldiv also useful
> - muldiv not supported natively by H8
I'm not surprised that MulDiv isn't supported directly by the H8. But do
you know if the H8's MULtiply instruction returns a 32-bit value? (On
16-bit 80x86 processors, for example, this is done using two registers: AX
for the low word and DX for the high word of the result.) I believe that
this would be a requirement for implementing a MULDIV byte code on the RCX.
> - have you considered writing native code?
I actually have considered writing native H8 code. Unfortunately, I have
been stymied by several factors:
1. The web link from the Lego Mindstorms Internals web page to the
"Download H8 Software Manual" appears to be broken. I spent awhile scouring
Hitachi's web page for this vital document without success. (If anyone
knows a current URL for this, I would be eternally grateful.)
2. I haven't yet gotten LegOs installed. I'm not sure if there's a
problem with the latest TAR file that I downloaded, but whenever I try to
expand it, I get errors. (I am running out of disk space, but it appears
that the TAR file is expanding in size by a factor of ten before that
happens which makes me suspicious that the file might be corrupted.)
3. I don't have the GCC environment loaded either. (What can I say,
I'm a Windows dweeb.) I've been looking for a good excuse to install Linux
on one of my old machines, and this might be it.
I do plan on conquering all of these problems in the very near future,
though, since I quickly realized that the standard Lego firmware isn't going
to keep up with me for very long. And after all, my offer to help write a
new & improved firmware wouldn't hold much water if I wasn't planning to get
set up to write H8 code.
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