Re: Sound-makes only one click?

[nparker@ssil.uoregon.edu (Neil Parker)]

In article <362e4a64.1108849@news.bright.net>,
Jm <j_2001_m@dejanews.com> wrote:
>I have a program programming sound on my apple 2c. This is an exact
>transscript of what I typed.
>
>(turn on computer)
>(says "Check disk Drive")
>CTRL-RESET
>CALL -151
>(at monitor)
>!
>(at mini assembler)
>8500:LDA C036
> JMP 8500
>(blank line)
>8500G
>
>Instead of getting some kind of tone, I just get a single click...then
>silence and blackness until I push ctrl-break then it beeps and goes
>back into basic like usual. What could be wrong here? I know there's
>nothing wrong with the hardware because the computer beeps, plays
>music, etc in games. thank you!

The problem is you're trying to toggle the speaker too fast.  Your code
toggles the speaker once every 7 microseconds, which is *much* faster than
the speaker is physically capable of responding to.  You need to put some
kind of delay into the loop.

Like this, for example:

8500:LDA C030
 LDX #0
 JSR FB1E
 JMP 8500

That delays using a call to PREAD, the paddle-reading subroutine.  The
amount of time that PREAD takes depends strongly on the current setting of
paddle 0, so you get a tone that changes when you move your paddle or
joystick.  (This program can make some *really* annoying sounds...)

               - Neil Parker

P.S.  You should always use $C030 to access the speaker, not $C036.
Location $C030 is guaranteed to always be connected to the speaker, but on
some Apple II's (the IIGS, for example), accessing $C036 just gets you
silence (and the current system speed settings).
-- 
Neil Parker, nparker@ssil.uoregon.edu, nparker@axis.llx.com,
http://axis.llx.com/~nparker/     (Note new addresses and home page!)

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