Re: [cc65] Uniform mass storage device discovery and file locations

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Sent from mobile phone (so please have understanding)

On 20 sie 2012, at 14:08, Oliver Schmidt <ol.sc@web.de> wrote:

> Hi,
> 
> Just for the records - here's again the code snipet and my questions -
> which the answer below refers to...
> 
> lda <device>
> jsr $ffb1 ; listen
> lda #$00
> sta $90   ; necessary ?
> lda #$ff  ; or rather #$6f ?
> jsr $ff93 ; lstnsa
> ldy $90
> jsr $ffae ; unlstn
> tya
> bpl <present>
> <not present>
> 
> However I have several questions:
> - Is it really necessary to initialize $90
> - What is the right high nibble for "opening" the cmd channel here $F or $6 ?
> - Is it correct to assume that unlstn doesn't trash Y ?
> - Is it correct that $90 must be saved before calling unlstn ?
> 
>> P. S. Unless someone replies earlier, I would need a few days (travelling now) to check my stuff at home to answer the questions about status ($90) byte. My bet is that answer to both is "yes" but have to double check the reasons, which I sort of only recall now - so don't take them as true and correct. [*]
>> 
>> * - 1) to start afresh, 2) to allow particular bits to be affected without losing previous information from the other ones
> 
> As noone else has answered yet I'd for sure appreciate if you would
> take the time after your return to re-check !
> 
> The code linked to a few posting back
> (http://codebase64.org/doku.php?id=base:detect_drives_on_iec_bus) sets
> the status to zero before calling LISTEN while mine above does it
> after that call. I'm not sure if this is of significance. Could LISTEN
> already fail (and set the status ?). Would LSTNSA probably even reset
> the status back to zero? ...?
> 
> It would be great to know the really correct sequence here!

Yes, I really appreciate your attention to details (not the first time ;-)

I should be back on 30th. 

Regards.

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