Hello,

I have a perplexity that is bugging me. It's in regards to Microchip's
AN566 - "Using the PORTB Interrupt on Change as an External Interrupt."

It's interesting, but I'm curious about their coding. I know Microchip has
made coding errors in the past, so I just hope someone can clarify something
for me.

The code they have for Example 2:

PER_INT BTFSS INTCON, RBIF ; PortB interrupt?

GOTO OTHER_INT ; Other interrupt

BTFSC PORTB, RB7     ;Check for rising edge
GOTO CLR_RBINTF   ;Falling edge, clear PortB int
:                                      ; flag
:                                     ;Do task for INT on RB7
:
CLR_RBINTF MOVF PORTB, 1 ; Read PortB (to itself) to end  mismatch condition

BCF INTCON, RBIF ; Clear the RB interrupt flag.

RETFIE ; Return from interrupt
OTHER_INT : ; Do what you need to here
:
RETFIE ; Return from interrupt

According to the app note, the ISR will run the needed code on the rising
edge of a wide pulse and ignore the falling edge. I've gone over this
hundreds of times and can't figure why they used BTFSC. Looking at the code
tells me that the ISR will run when RB7 is low, which would be a falling
edge, right?

At this point, I've looked at the appnote/code so many times that it's just
a blur. So, can someone clarify that snippet for me? Did Microchip make a
goof?

Thanks,

Tim

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