I have two identical MB's both using XP Pro w/sp2
They are the Foxconn N570SM2AA.

I also have two serial devices (a FTA receiver and a RF signal level meter) that I have to first disable the serial port, then re-enable it to be able to communicate with either. If I don't get a error message.

The previous MB had a nForce2 chipset and used 2k. I had no issue with two different FTA receivers and the serial port.

I have another piece of test equipment which uses a serial port, but there is a different problem with the software locking up after 5 seconds after hitting the 'start' button to try to connect with the device. I believe this is another issue as there was no issue with the previous MB and O/S.

Any ideas about why I have to disable, then re-enable the port everytime?
BTW; no conflicts in DM and it is the stock Windows driver that is loaded.

What you may be running into is a problem with the serial controller chip itself

Volvo and Mack also use a serial connector to interface with Engine ECU's

The Software Required the Old RS232 standard using Uart 8250 and 16450 and it's specific requirements

Both refused to work with ANY of the newer chips 16550 and 16550A

We solved this with two systems ( in Two shops )
One had the Older chip in it and dual booted it
one with win2K for the mack and XP for the Volvo

The second was to find and add in an old serial port card that True 16450 chips on it

Older and slower than the newest chips out
but it was the only way we could cure it..

I Think if you check you will find your com ports are running a new chip that is 16550A compatible

Check your software requirements
Then match the comport settings and LOCK them at that
the old 8 non and 1 for example

They have been at the default settings.
The FTA receiver only has a rate setting (if I remember correctly and that is through the s/w), the SLM (Signal Level meter) has rate, parity, flow, terminator & echo in the meter, but just the rate in the sw.

Not sure what terminator & echo does since I never saw those before. The s/w was orginally written in '93. :eek:

9600 8 non and 1
for years was the default for almost everything
9600,8,1 and1 was the other

Also the ground was a major headache in the past with many com devices
Even down to the modems of years past


Sorry I can't be of more help

Ok, it apperas it was some issue with the IRQ.

Elsewhere it was suggested to set the serial port in the bios to manual, 3F8, IRQ4 and to set the PCI bus to manual.

I looked in the bios, the serial port was already set to manual, 3F8 & IRQ4. When I looked at Device Mgr. before I went into the bios, resources were 3F8, but IRQ7.

I only changed the PnP/PCI settings to manual from auto.

This appears to work.

If the serial port was already set to manual, was it the fact the PnP/PCI was set to auto what overrided this? :confused:

yes.
PCI at auto allows it to share an irq or be reset by the PCI selection to any irq
hence the IRQ 4 in one setting and IRQ7 in another
The software was using 4 and the buss was using 7

Ok, but why does a disable/enable change the IRQ?

When you enable auto in the PCI buss
It allows the PCI to auto change anything it wants to allow sharing

This can cause and or allow any number of Devices to use One IRQ

The idea was to allow More devices

What in fact happened in your case and in my own in the past

PCI Auto select put almost everything onto one or two IRQ and used the remainder to allow/control sharing

This can and does cause problems with NON sharing devices
Mouse,modems, and as you have found out Com port attached devices

I understand that, but that didn't answer my previous question of why re-enabling the disabled posrt sets the port back to IRQ4? I never looked, but i assume it was #4.
Why didn't/wouldn't it put it back to what it was?

Good question

The Answer
Welcome to windows

Did windows force it to read the Bios setting for the Com port and Not the PCI ?
More than likely
But that is only a guess

I'm glad I used the term "appears".
It isn't working anymore. I'm back to square one. DM reports IRQ4, but I get the same comm. error message. :mad:

If I disable then re-enable the port the 1st time, there is no reboot message. If I do this a 2nd time, I get the reboot message.
On my other bootable drive, I alway get the reboot message.

Any idea why?

In Windows when it works once and not again or it doesn't accept the change or even recognize it
it doesn't prompt for the reboot

In other instances it sees the change and then does recognize it as a change
But the default being reentered

Windows anything does not deal well with old school technology ..
NON plug and play anything gives it hiccups

Mix plug and pray hardware with NON plug and play software and windoz goes to sleep

As I posted above the ONLY cure I was able to find was to add a com port card with true non plug and play hardware and dual boot it with two operating systems..
Forcing windoz to behave with the hardware

On HDD one I can do a disable/enable once with no issue. If I try to do so again, it wants me to reboot.
On HDD two, I have to do a reboot the very first time. Both have identical O/S'es off the same slipstreamed sp2 install disc.

I will look for a PCI serial port card since there are two many 'strang' issues with the on board port. It just pisses me off since I specifically got the MB for the ability of the serial port since many don't have that anymore.
I know it isn't a big deal untill I started looking at some of the prices for PCI serial port cards. I've seen them for over $100. :rolleyes:

Are they on drugs? Can I get some? :D

I also found some for $9. which is all of what they are worth.

I also found some for $9. which is all of what they are worth.


Better check the chips installed before you order them

Specifically the Uart

What? Too cheap? What should I look for?

No, they may be too new...

To new?? Which, the cheapos or the more expensive ones?

The expensive ones would most likely be at least 16550s...

The cheap ones...make sure they are true 16450 and not 16550 emulating a 450.

The ones I was looking at have this chip. Can I assume this is a cheaper chip you spoke of;
16C550 compatible UART with 16byte transmit-receive FIFO Multi – card capabilityIf fact most have this. The more expensive ones have a 16550, 16660 and some have the 16950.
I came across this tidbit;
http://tldp.org/HOWTO/Serial-HOWTO-19.html

Does that sum it up? Since my two devices are a somewhat older design (roughly 10 years old), would a newer serial chip be some kind of disavantage?

Between the IRQ sharing that more modern serial controllers are capable of and the FIFO it is most likely the cause for the problem.

The older cards, most of which would be ISA (which isn't going to help any with a board that is probably PCI), commandeered an IRQ, with the ISA boards you hard set the IRQ by way of a jumper, and told Plug and Pray to go get stuffed...they kept that IRQ until you physically changed it. windows couldn't do squat about it and assigned everything else around that fact.

The FIFO, on the other hand may be 'too much' for the equipment to handle...if it isn't expecting any sort of buffering then it will end up confused, especially if it is sitting there transmitting and the buffer is full and it isn't acknowledging that it has to wait...

But that doesn't seem to be your problem...the main problem seems to be IRQ/PnP related. Which, to solve, you will either need to run an OS that allows you to actually control IRQs (Win2k allows more user control than XP) or a motherboard/controller card that allows you to 'hard' assign the IRQ in such a way that the OS can't change it.

When dealing with computer controlled/read test equipment upgrading to more modern OS/hardware is very often not an option. No matter how much 'they' claim to have 'backwards compatibility' it is never enough to have said equipment operate correctly.

With these choices to start with (no single port cards), what would be a good choice;
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=2000010073%201187112434&bop=And&Order=PRICE

Seems to be the 16C550 vs 16650 (at 2x the cost).

Do you have a link to a data sheet/manual for one of the problem units? It may be easier to go through a spec sheet and try and come up with a recommended card that way...

Here is the MB, since that is the current serial port that I have;
http://www.foxconnchannel.com/en-us/product/Motherboards/detail_overview.aspx?ID=en-gb0000205

I assume it is the Southbridge where the Com 1 comes from.

The SLM is a Tektronix/Tempo RFM151. Support has been discountinued from the manufacture. I can't find a Service Manual for it either. The orginal design is around 10 years old. I'm pretty sure it is a issue with the meter sending data back. It just started to act up. There is no available external reset.

The forums ridiculous 19k limit on upload file sizes prevents me from posting the spec sheet.