COM1 IRQ and I/O Port greyed out

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Recoil
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Joined: 7. Sep 2022, 23:36

COM1 IRQ and I/O Port greyed out

Post by Recoil »

Hi Folks,
I am trying to set up old software for an industrial calibration laser. I did install Windows XP in VirtualBox, the host PC is Windows 10. I am trying to setup "COM1" for the calibration software.
The calibration software has a list of "I/O addresses" (please look at attachment) that it could use to communicate with the laser. I see in VirtualBox settings that COM1 has the I/O address set to 0x3F8 but is greyed out along with IRQ and I can't change it. Is there a way to be able to assign an address that will work with the software? Thank you all in advance.
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Port Address.png
Port Address.png (2.97 KiB) Viewed 1775 times
scottgus1
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Re: COM1 IRQ and I/O Port greyed out

Post by scottgus1 »

The Virtualbox settings will probably not work until the VM is shut down completely (will say "powered off" in the status line under the VM name in the list in the main Virtualbox window). Changing this sort of setting is like pulling the hardware out of a PC, which most PCs don't like when they're running.

This may also help: How to: Add a Serial Port in Windows XP and 7 Guest
mpack
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Re: COM1 IRQ and I/O Port greyed out

Post by mpack »

3F8H/4 is the standard base_address/IRQ for COM1, so if the software was ever intended to work on standard PCs then it should be able to accept that address.

But the trick to entering a non-standard base address is to select "User-defined" as the port id. As mentioned, COM1 is by definition == 3F8H/4.

It's a pity you cropped that screenshot so much, as I don't understand why it shows two numbers. A base address only needs one number. And the second column does not show IRQ numbers (those only go up to 15 and for serial ports are always 4 or 3 anyway, since most other IRQs have other assignments). It seems to be implying that some register is 16 bits wide, which is not the case for the PC 8250/16550 UART. If your software is expecting non-standard hardware then it won't work in a VM, at least unless you are capable of developing a simulation of that hardware for VirtualBox.
Recoil
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Re: COM1 IRQ and I/O Port greyed out

Post by Recoil »

Hi folks thank you very much for the replies. Yes I did saw that from other threads that I need it to turn the VM off before making any changes however, even with the VM powered down those fields are greyed out. thank you for the tip tho.
I am attaching a screenshot of the port address selection in the software, hope it helps to get a better idea. The software ran in a vintage PC with an ISA card to connect the RS232. In this card you could select a range of addresses with 3 DIP switches (SW1, SW23 SW3) that is why you see 2 columns of addresses.
I think at some point I read in the manual that any of those address ranges will work the software is listening on those I/O addresses. Anyhow hope that sheds some light in the issue. Thank you again for your help.
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Port Address.png
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mpack
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Re: COM1 IRQ and I/O Port greyed out

Post by mpack »

See the second paragraph of my previous reply - you seem to have missed it.

Your explanation of the second column still makes no sense to me. The traditional UART address (e.g. 0x3F8) identifies the base of an 8 byte sequence of 8-bit registers in I/O address space (see https://en.wikibooks.org/wiki/Serial_Pr ... _Registers). So both addresses listed are in the same address space. The first number is the write address, the second number is the interrupt id reg - but since the latter is always at base+2 I don't understand why it (and none of the other regs) is listed as a separate address. And if it is just a standard UART then why are standard PC UART addresses not selectable? It all makes me think that info is missing, or a misunderstanding is happening. I'd be much happier if the dialog caption specifically said "UART Base address and IRQ".

I can't promise that VirtualBox will be agnostic when it comes to which I/O addresses you can use: that rather assumes that nothing else is already using those alternate addresses. That said, this page (http://ps-2.kev009.com/eprmhtml/eprma/926.htm) does seem to show those I/O ranges as available.
Recoil
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Joined: 7. Sep 2022, 23:36

Re: COM1 IRQ and I/O Port greyed out

Post by Recoil »

Thank you very much for all your help Mpack. I thought for what I could remember those where ranges of address but I am sure you can understand this things better than me.
I will read the links you posted and see if I can understand better what I am looking at. Once more thank you for your input!
fth0
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Re: COM1 IRQ and I/O Port greyed out

Post by fth0 »

Recoil wrote:ISA card to connect the RS232
Are you sure? It could also be an ISA card for RS-422/485. Can you tell us the name of the ISA card or post a picture? Can you name the industrial calibration laser or the software?
Recoil wrote:In this card you could select a range of addresses with 3 DIP switches (SW1, SW23 SW3) that is why you see 2 columns of addresses.
What's the relationship of the configurable radio button and the 3 DIP switches? Are you supposed to tell the software which switches you've turned on/off on the hardware? Also, please explain your reasoning for the 2 addresses. I don't understand that either. ;)

PS: Regarding the I/O port addresses, I've also checked the RBIL without success.
mpack
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Re: COM1 IRQ and I/O Port greyed out

Post by mpack »

I was thinking about this overnight.

I think the simplest explanation for the weird dialog is that the programmer who designed the dialog was not a hardware guy and he didn't know anything about UARTs. He would not be the same guy who designed the ISA card itself, and probably not the laser calibration software either. And the reason why the standard base addresses are omitted is because the ISA card was designed to be plugged into a standard PC of the DOS or early Windows era, which would therefore have one or two UARTs already present on the motherboard (even today that feature is IME often present on the motherboard of a tower/midi PC even if not connected to the backplane).

So the only remaining questions are: (1) is this truly the COM port selection dialog, or is this actually configuring the ISA card driver while the software's COM port selection will be elsewhere. (2) Is there something non-standard about the ISA card UART? Note that even if it uses an backwards compatible UART (say, a 16550), it could be using a different baud rate clock to allow higher data rates. ISTR that was a common reason to buy addition UART cards, the other being to get multiple ports, e.g. 4-port or 8-port cards served by a single interrupt handler not shared with the standard UARTs.
klaus
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Re: COM1 IRQ and I/O Port greyed out

Post by klaus »

If it's really a 8250/16450/16550 type UART (it could be that the programmer just considered the data and IIR ports as important enough to mention) then it should be purely a matter of picking "User-defined" for the Port number in the settings. Then you can enter 0x280 or such...
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