Subject:
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Re: Kent's sonar routines
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Fri, 13 Mar 1998 04:24:21 GMT
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Original-From:
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Max Davies <[mdavies@cam.org]SayNoToSpam[]>
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Viewed:
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1407 times
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MAR ERICSON wrote:
> Can anyone clarify something for me?
>
> A section of the code of sonar.asm goes as
> follows:
>
> variable_sonar_time
> sonar_time FDB 0
>
> What does this mean? Why are there two variables
> before the FDB?
The line "variable_sonar_time" indicates that the
immediately following FDB will be available to IC
as an integer variable named "sonar_time".
The next line with the FDB is just a regular
assembler definition statement to allocate storage
for the variable and name it for assembler access
purposes.
> Another section goes as follows:
>
> variable_sonar_enable FCB 0
> sonar_enable FCB 0
>
> I thought IC integers had to be 2 bytes.
Yes, IC integers have to be 2 bytes.
> And also, are these two different variables?
My guess is "yes and no". I am guessing they are
pulling a trick so that IC sees a 2-byte variable
while assembler sees a 1-byte variable.
I haven't seen this sort of thing before. If you
didn't copy it wrong and if it really works then
my guess would be that it is defining a
single-byte value for assembler usage, prefixed by
a guaranteed null byte so that IC can access it
properly.
/Max
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Message is in Reply To:
 | | Kent's sonar routines
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| Can anyone clarify something for me? A section of the code of sonar.asm goes as follows: variable_sonar_time sonar_time FDB 0 What does this mean? Why are there two variables before the FDB? Another section goes as follows: variable_sonar_enable FCB (...) (27 years ago, 13-Mar-98, to lugnet.robotics.handyboard)
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