Date: Mon, 30 Dec 1996 19:06:52 -0900 (AKST) From: hmmm <hmmm@alaska.net> To: Bruce Evans <bde@zeta.org.au> Cc: hackers@freebsd.org Subject: Re: Ints Message-ID: <Pine.GSO.3.93.961230184937.6958A-100000@calvino.alaska.net> In-Reply-To: <199612302312.KAA13090@godzilla.zeta.org.au>
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On Tue, 31 Dec 1996, Bruce Evans wrote: > >IE - are any interrupt functions/bits LATCHED - that may need to be > They are not latched by ISA hardware. They are latched by FreeBSD > software, except for some serial interrupts. ok - but since ---I--- am the ISR - i would know about any interrupt conditions before FreeBSD ... right? anyway - i have this on my own OS that doesn't care ... > >for example - i have both COM ports tied to the same ISR - is there any > >danger in reading RxBuf1 (lower priority) while SERVICING an RxBuf2 INT? > There is extreme danger of this not working at all, for other reasons - > ISA hardware doesn't support sharing interrupts (at the same time). this i have heard - but cannot comprehend! the UART will activate its IRQ - negotiate with the PIC - and when the PIC acks everything it INTerrupts the CPU to picks up a vector in RAM to jump to ... who cares if the address is the same ISR or not ??? i don't understand! :)
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