Date: Thu, 03 May 2001 11:49:37 -0600 From: Brett Glass <brett@lariat.org> To: Terry Lambert <tlambert@primenet.com>, dchulhan@uwi.tt (Dale Chulhan - Home) Cc: chat@FreeBSD.ORG (chat@FreeBSD.ORG) Subject: Re: Modem Woes Message-ID: <4.3.2.7.2.20010503114324.0459d260@localhost> In-Reply-To: <200105031734.KAA20670@usr02.primenet.com> References: <3AF14814.B259D186@uwi.tt>
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At 11:34 AM 5/3/2001, Terry Lambert wrote: >In FreeBSD, COM ports can not share IRQs. Terry, this is not correct. I have several multiport cards in which several UARTs share IRQs. They all run fine under FreeBSD. Here's an excerpt from the kernel config of one of them: device sio2 at isa? port "IO_COM3" tty flags 0x585 vector siointr device sio3 at isa? port "IO_COM4" tty flags 0x585 vector siointr device sio4 at isa? port 0x1f8 tty flags 0x585 vector siointr device sio5 at isa? port 0x1e8 tty flags 0x585 irq 9 vector siointr All of them share IRQ 9. >If your modem is COM4: in Windows, it uses IRQ 3, which is >already allocated to COM2:. Attempting to share IRQs between ports can cause an electrical problem on the bus IF the ports are on two separate ISA cards, because the IRQ lines on ISA are tri-state, not open collector. But if the UARTS are on EISA or PCI cards, or on the same card, an IRQ can be shared. >Note that Windows can "share" IRQs 4 and 3 (COM1: IRQ 4, >COM2: IRQ 3, COM3: IRQ 4, COM4: IRQ 3) because it does not >open both COM1: and COM3: or COM2: and COM4: simultaneously. I've had comm ports that shared IRQs open simultaneously under Windows. --Brett To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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