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I'm using a 4 port serial card (ISA) with Win98SE and VB5 with the

MSComm control. I want to be able to constantly access all 4 ports at

the same time (checking for characters). COM1 AND COM3 are using IRQ4

and COM2 and COM4 are using IRQ3. I can't seem to be able change

these IRQs so they are all different.



The problem is that when I try to access say COM1 and COM3 at the same

time, the system hangs. I have to break into the program to get out

of it. If I only use COM1 and COM2 (which are different IRQs) it

works fine. Is there any way around this? Would a PCI card be any

better? Or is there any other solution or type of card which will

solve my problem?



I would appreciate any help.



Regards



Karl





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Sorry, can't help you resolve your problem, but I can tell

you that COM1-3 and COM2-4 share IRQs because that's the

way that the hardware's built. You won't be able to

separate them.

I might be wrong on this (it's been waaaay too many years since I've played

with COM ports), but my recollection is that COM1 and COM3 (which share an

interrupt) cannot be in use at the same time (and the same for COM2 and

COM4). The interrupt is "assigned" to the first of the twin, shared ports in

use and the other is blocked... or something like that.



Rick - MVP





"Steve" <junkmail@aol.com>wrote in message



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With the multi port ISA serial cards I've used there has

always been a jumper to select the IRQ's. You need to

check your system configuration to see if you have any

available. Then you just use the device manager to match

it up with your IRQ.



I have recently used USB to Serial converters with no

problems and they are very easy to set up. There are

others but I have purchased (word wrapped link):



www.kontron.com/products/pdproductsubcategory.cfm?">www.kontron.com/products/pdproductsubcategory.cfm?

keyProductCategory=8&kps=785



Dick Grier's site may be of additional help:



www.hardandsoftware.net



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I recently bought one of these (USB<->RS232), it works great... (watch for

word wrap)

Only $25 Cdn...



http://linhaw.com/?page" rel="nofollow" target="_blank">linhaw.com/=shop/flypage&product_id=2064&category_id=ecd5fb63858

4a66eddeee0491def821f&ps_session=3084733d816caa59113f91100d0c11d5



Norvin



"fred" <fred@fred.com>wrote in message



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Hi,



You have to use serial port hardware that support separate interrupts.

These are available. There is no way to share interrupts.



--

Richard Grier (Microsoft Visual Basic MVP)



See www.hardandsoftware.net for contact information.



Author of Visual Basic Programmer's Guide to Serial Communications, 3rd

Edition ISBN 1-890422-27-4 (391 pages) published February 2002.





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With ISA based serial adapters, COM1 and COM3 usually share an IRQ and

COM2 and COM4 also share an IRQ.

The newer PCI based add-on serial adapters use a single IRQ for all

ports without any conflicts. Also, the USB based add-on serial

adapters do not use an IRQ at all because they use the USB subsystem

along with a virtual COM port driver to do all I/O.

You can purchase both PCI and USB based add-on serial adapters from:

TAL Technologies. Visit the following URL for more information:

www.taltech.com/TALtech_web/products/rs232.html">www.taltech.com/TALtech_web/products/rs232.html







On Wed, 13 Aug 2003 11:52:24 +0100, Servicecare Technology Ltd

<sales@servcare.demon.co.uk>wrote:



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