On Sep 3, 2011, at 5:57 PM, Nathan House wrote:

>> RCIF is a read-only bit.  You cannot write a zero to it.
>
> Isn't that unusual for an interrupt flag? Don't interrupt flags
> generally have to be cleared, else the ISR will continually be called?

Yes; many interrupt controllers and some raw interrupt sources will =20
require that you specifically reset the appropriate bit.  However, =20
that tends to be for peripherals that are less obviously connected to =20
the reasons for their interrupts.  It's pretty common for UART =20
interrupt flags to be cleared automatically when the code takes the =20
appropriate action.

> Does reading from the RCREG (like "variable =3D RCREG") clear the
> interrupt flag, then?

Yes, exactly.  This is probably backward compatible with some ancient =20
UART chip or something.  I've seen some uarts where less obvious =20
interrupt sources (modem control line changes, error conditions) have =20
to be explicitly reset...

BillW


--=20
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