Dallas IButton 1990 Presence pulse

[Darrel Taylor]

I'm not sure why this isn't in the manual. Maybe they just forgot it was there.

You can have an optional Label after the OneWire commands.
If the Presence pulse isn't received after the reset, it will jump to that label.

This line will simply detect presence or not without trying to send data.

OWOUT DQ, 1, [], NotThere  ; Detect if OW device is present
 ... 
NotThere:

ADDED: Or, since you are using a ROM only device, you can do the same thing with OWIN. Saves a little code space.
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