Re: Tape input to speaker

[Simon Williams <DONTemail@luddite.ca>]

On 23 Sep 2002 02:48:11 GMT mjmahon@aol.com (Michael J. Mahon) wrote:

> loop      lda cassin   ;Read the cassette input
>           eor oldcass   ;Compare with previous state (hi bit)
>           bpl nochange  ;Hi-bit off if no change
>           sta oldcass   ;Save the new state
>           sta spkr      ;Flip the speaker
>           bmi loop      ;Branch always.
> 
> nochange  pha     ;Kill 7 cycles
>           pla
>           jmp loop

Well, I basically understand how that works (minor miracle), but I'm at a loss with
line 2... does *oldcass* refer to a specific location in memory?  I understand that 
the condition of bit 7 of $C060 is what is important, but I'm not sure how that
information is arrived at or where it might be found... 

SW