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Path: sserve!newshost.anu.edu.au!munnari.oz.au!news.Hawaii.Edu!ames!agate!spool.mu.edu!uunet!mcsun!sun4nl!tuegate.tue.nl!svin09.info.win.tue.nl!wzv.win.tue.nl!gvr.win.tue.nl!guido From: guido@gvr.win.tue.nl (Guido van Rooij) Newsgroups: comp.os.386bsd.questions Subject: Re: Modem setup on 386BSD [and a further QUESTION] Date: 29 May 1993 16:04:37 GMT Organization: Eindhoven University of Technology, The Netherlands Lines: 45 Distribution: world Message-ID: <1u81il$o45@wzv.win.tue.nl> References: <1993May27.043819.13711@mcshub.dcss.mcmaster.ca> <CJB.93May28115334@thrip.cs.uq.oz.au> <1993May28.195017.23712@fcom.cc.utah.edu> NNTP-Posting-Host: gvr.win.tue.nl terry@cs.weber.edu (A Wizard of Earth C) writes: >In article <CJB.93May28115334@thrip.cs.uq.oz.au> cjb@cs.uq.oz.au (Christopher J Biggs) writes: >>Question: Has anyone got a driver that will drive a multi-IO card at IRQ 2&3 >>and an internal modem on 2or3 (it wont go anywhere else!!). >I haven't seen one yet -- and, unless you have a very special modem and com >card, you aren't going to be able to write one -- ever. >Interrrupt sharing depnds on being able to ask all devices using the >interrupt if they were the one that caused the interrupt -- basically, >the interrupt is a "data available" flag. Most serial hardware doesn't >support a flag to indicate data available since last read. Multiport Not true. The 8250, 16440, 16450 and friends all have a bit telling if this UART triggered the interrupt. (bit 0 in the IIR register). The reason you can't share interrupts between cards in different slots in an isabus system is the fact that you can break your hardware: if one card generates an interrupt it wants to hold up, say, the isa bus's irq 3 line. But the other card is holding the same line down. Unless you designed your system such that this is allowed, normally you have problems. >boards, on the other hand, *do* support flagging the interrupt source, >*but* require a driver that knows about the flagging mechanism. Some >UARTS (but not the low-end ones in most PCs) support a status register >indicating "data in FIFO". This can be used the same way as a hardware >specific interrupt origin flag (like most multiport boards use), but >the hardware specific flags are not frequently in the same place between >multiple hardware vendors, so a special driver is normally needed with >at least a vendor- (and potentially a product-) specific piece of code >to query interrupt origin. > Terry Lambert > terry@icarus.weber.edu >--- >Any opinions in this posting are my own and not those of my present >or previous employers. -Guido -- Guido van Rooij | Internet: guido@gvr.win.tue.nl Bisschopsmolen 16 | Phone: ++31.40.461433 5612 DS Eindhoven | ((12+144+20)+3*sqrt(4))/7 The Netherlands | +(5*11)=9^2+0