So you only need to read this if you're having problems or if you want to understand how it works. The driver must of course know both the IO address and IRQ so that it can talk to the serial port chip. Modern serial port drivers kernel 2.
But unfortunately, there is some PCI serial port hardware that the driver doesn't recognize so you might need to enable the port yourself.
See PCI: Enabling a disabled port. For the old ISA bus, the driver also probes likely serial port addresses to see if there are any serial ports there.
It's often automatically done by the serial driver but sometimes you have to do it yourself. What follows repeats what was said above but in more detail.
And the driver needs to call this pair a name such as ttyS2. We could call this "io-irq" configuring for short. The old way is using the "setserial" program to tell the driver.
If you need to configure but don't understand certain details it's easy to get into trouble. When Linux starts, an effort is made to detect and configure low-level the serial ports. If the serial ports work OK, there may be no need for you to do any more low-level configuring. If you're having problems with the serial ports, then you may need to do low-level configuring.
If you have kernel 2. Starting with kernel 2. It may be just as easy to give each port a unique interrupt if they are available. See Interrupt sharing and Kernels 2. The low-level configuring setting the IRQ and IO address seems to cause people more trouble than the high-level stuff, although for many it's fully automatic and there is no configuring to be done. Until the port is enabled and the serial driver knows the correct IRQ and IO address, the port will not usually not work at all.
Applications, and utilities such as "setserial" and "scanport" Debian only?? Even if an ISA port can be found by the probing done by the serial driver it may work extremely slow if the IRQ is wrong. See Extremely Slow: Text appears on the screen slowly after long delays. IO address, IRQs, etc.
But there are many other types of "resources" so the term has many other meanings. In summary, the low-level configuring consists of enabling the device, giving it a name ttyS2 for example and putting two values an IRQ number and IO address into two places:. The device driver done by PnP or " setserial " Configuration registers of the serial port hardware itself, done by PnP software or jumpers on legacy hardware. They are usually correct.
But if you're having problems, your serial port may not show up at all or if you do see a message from "setserial" it may not show the true configuration of the hardware and it is not necessarily supposed to. Some PCI serial ports can be automatically detected and low-level configured by the serial driver. Others may not be. While kernel 2. So you don't need to use "setserial" for it. There is a possible problem if you don't use the device filesystem.
PCI ports are not well standardized. Some use main memory for communication with the PC. Some require special enabling of the IRQ. The output of "lspci -vv" can help determine if one can be supported. This is different than the probing of IO addresses by the serial driver which means reading certain IO addresses to see if what's read looks like there's a serial port at that address. What the device driver thinks has been set This is what setserial usually sets and shows.
What is actually set in the hardware. Both 1. If they're not it spells trouble since the driver has incorrect info on the physical serial port. If the driver has the wrong IO address it will try to send data to a non-existing serial port --or even worse, to some other device.
What happens if a serial cable is not working properly? This issue can limit data transmission and retrieval but can be easily fixed by replacing the serial cable. In many cases, a loose cable may simple need to be reconnected to a serial port. But in other situations, an ineffective cable will need to be replaced immediately, especially if the serial port is functioning properly.
A software driver may result in a non-working serial port. If this driver is not installed properly or is not compatible with a serial port, it may cease to perform. Re-installing the affected drivers can help a user overcome this problem. In addition, a user may be able to alter the serial port settings to ensure this issue is fully resolved.
It was mainly used for modems. The cua major number was 5 andminor numbers started at Older serial drivers ? The tables below shows some examples of serial device names. For more info see the usb subdirectory in the kernel documentationdirectory for files: usb-serial, acm, etc. The newer lock file system doesn't fall intothis trap so it's now OK to use such links. Inspecting the connectors may give some clues but is often notdefinitive.
The serial connectors on the back side of a PC areusually DB connectors with male pins. There may be one9-pin perhaps ttyS0?? For two9-pin ones the top one might be ttyS0. If you only have one serial port connector on the back of your PC,this may be easy.
If you also have an internal modem, a program likewvdial may be able to tell you what port it's on unless it's a PnPthat hasn't been enabled yet. A report from setserial atboot-time or run by you from the command line should help youidentify the non-modem ports. If you have two serial ports it may be more difficult. You could haveonly one serial connector but actually have 2 ports, one of whichisn't used but it's still there electronically. First check manuals if any for your computer.
Look at the connectors for meaningfullabels. Thank you for your kind reply. I would highly appreciate if you would take remote access over the two computers and kindly have a look. Is there any mobile number or email to contact you? Browse Community. Turn on suggestions. Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type. Showing results for. Search instead for. Did you mean:. Could anyone please tell me how can I find that?
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