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SETSERIAL !!!SETSERIAL NAME SYNOPSIS DESCRIPTION OPTIONS PARAMETERS CONSIDERATIONS OF CONFIGURING SERIAL PORTS MULTIPORT CONFIGURATION Hayes ESP Configuration CAUTION FILES SEE ALSO AUTHOR ---- !!NAME setserial - get/set Linux serial port information !!SYNOPSIS __setserial [[ -abqvVWz ]__ device __[[__ parameter1 __[[__ arg __] ] ...__ __setserial -g [[ -abGv ]__ device1 ... !!DESCRIPTION __setserial__ is a program designed to set and/or report the configuration information associated with a serial port. This information includes what I/O port and IRQ a particular serial port is using, and whether or not the break key should be interpreted as the Secure Attention Key, and so on. During the normal bootup process, only COM ports 1-4 are initialized, using the default I/O ports and IRQ values, as listed below. In order to initialize any additional serial ports, or to change the COM 1-4 ports to a nonstadard configuration, the __setserial__ program should be used. Typically it is called from an ''setserial'' script, which is usually run out of ''/etc/init.d''. The ''device'' argument or arguments specifies the serial device which should be configured or interrogated. It will usually have the following form: __/dev/ttyS[[0-3]__. If no parameters are specified, __setserial__ will print out the port type (i.e., 8250, 16450, 16550, 16550A, etc.), the hardware I/O port, the hardware IRQ line, its __ If the __-g__ option is given, the arguments to setserial are interpreted as a list of devices for which the characteristics of those devices should be printed. Without the __-g__ option, the first argument to setserial is interpreted as the device to be modified or characteristics to be printed, and any additional arguments are interpreted as parameters which should be assigned to that serial device. For the most part, superuser privilege is required to set the configuration parameters of a serial port. A few serial port parameters can be set by normal users, however, and these will be noted as exceptions in this manual page. !!OPTIONS __Setserial__ accepts the following options: __-a__ When reporting the configuration of a serial device, print all available information. __-b__ When reporting the configuration of a serial device, print a summary of the device's configuration, which might be suitable for printing during the bootup process, during the /etc/rc script. __-G__ Print out the configuration information of the serial port in a form which can be fed back to setserial as command-line arguments. __-q__ Be quiet. __Setserial__ will print fewer lines of output. __-v__ Be verbose. __Setserial__ will print additional status output. __-V__ Display version and exit. __-W__ Do wild interrupt initialization and exit. This option is no longer relevant in Linux kernels after version 2.1. __-z__ Zero out the serial flags before starting to set flags. This is related to the automatic saving of serial flags using the -G flag. !!PARAMETERS The following parameters can be assigned to a serial port. All argument values are assumed to be in decimal unless preceeded by __port__ port_number The __port__ option sets the I/O port, as described above. __irq__ irq_number The __irq__ option sets the hardware IRQ, as described above. __uart__ uart_type This option is used to set the UART type. The permitted types are __none__, 8250, 16450, 16550, 16550A, 16650, 16650V2, 16654, 16750, 16850, 16950, and 16954. Using UART type __none__ will disable the port. Some internal modems are billed as having a uart__ parameter, you will see dropped characters during file transmissions. These UART's usually have other problems: the __skip_test__ parameter also often must be specified. __autoconfig__ When this parameter is given, __setserial__ will ask the kernel to attempt to automatically configure the serial port. The I/O port must be correctly set; the kernel will attempt to determine the UART type, and if the __auto_irq__ parameter is set, Linux will attempt to automatically determine the IRQ. The __autoconfig__ parameter should be given after the __port__,__auto_irq__, and __skip_test__ parameters have been specified. __auto_irq__ During autoconfiguration, try to determine the IRQ. This feature is not guaranteed to always produce the correct result; some hardware configurations will fool the Linux kernel. It is generally safer not to use the __auto_irq__ feature, but rather to specify the IRQ to be used explicitly, using the __irq__ parameter. __^auto_irq__ During autoconfiguration, do ''not'' try to determine the IRQ. __skip_test__ During autoconfiguration, skip the UART test. Some internal modems do not have National Semiconductor compatible UART's, but have cheap imitations instead. Some of these cheasy imitations UART's do not fully support the loopback detection mode, which is used by the kernel to make sure there really is a UART at a particular address before attempting to configure it. So for certain internal modems you will need to specify this parameter so Linux can initialize the UART correctly. __^skip_test__ During autoconfiguration, do ''not'' skip the UART test. __baud_base__ baud_base This option sets the base baud rate, which is the clock frequency divided by 16. Normally this value is 115200, which is also the fastest baud rate which the UART can support. __spd_hi__ Use 57.6kb when the application requests 38.4kb. This parameter may be specified by a non-privileged user. __spd_vhi__ Use 115kb when the application requests 38.4kb. This parameter may be specified by a non-privileged user. __spd_shi__ Use 230kb when the application requests 38.4kb. This parameter may be specified by a non-privileged user. __spd_warp__ Use 460kb when the application requests 38.4kb. This parameter may be specified by a non-privileged user. __spd_cust__ Use the custom divisor to set the speed when the application requests 38.4kb. In this case, the baud rate is the __baud_base__ divided by the __divisor__. This parameter may be specified by a non-privileged user. __spd_normal__ Use 38.4kb when the application requests 38.4kb. This parameter may be specified by a non-privileged user. __divisor__ divisor This option sets the custom divison. This divisor will be used then the __spd_cust__ option is selected and the serial port is set to 38.4kb by the application. This parameter may be specified by a non-privileged user. __sak__ Set the break key at the Secure Attention Key. __^sak__ disable the Secure Attention Key. __fourport__ Configure the port as an AST Fourport card. __^fourport__ Disable AST Fourport configuration. __close_delay__ delay Specify the amount of time, in hundredths of a second, that DTR should remain low on a serial line after the callout device is closed, before the blocked dialin device raises DTR again. The default value of this option is 50, or a half-second delay. __closing_wait__ delay Specify the amount of time, in hundredths of a second, that the kernel should wait for data to be transmitted from the serial port while closing the port. If __session_lockout__ Lock out callout port (/dev/cuaXX) accesses across different sessions. That is, once a process has opened a port, do not allow a process with a different session ID to open that port until the first process has closed it. __^session_lockout__ Do not lock out callout port accesses across different sessions. __pgrp_lockout__ Lock out callout port (/dev/cuaXX) accesses across different process groups. That is, once a process has opened a port, do not allow a process in a different process group to open that port until the first process has closed it. __^pgrp_lockout__ Do not lock out callout port accesses across different process groups. __hup_notify__ Notify a process blocked on opening a dial in line when a process has finished using a callout line (either by closing it or by the serial line being hung up) by returning EAGAIN to the open. The application of this parameter is for getty's which are blocked on a serial port's dial in line. This allows the getty to reset the modem (which may have had its configuration modified by the application using the callout device) before blocking on the open again. __^hup_notify__ Do not notify a process blocked on opening a dial in line when the callout device is hung up. __split_termios__ Treat the termios settings used by the callout device and the termios settings used by the dialin devices as separate. __^split_termios__ Use the same termios structure to store both the dialin and callout ports. This is the default option. __callout_nohup__ If this particular serial port is opened as a callout device, do not hangup the tty when carrier detect is dropped. __^callout_nohup__ Do not skip hanging up the tty when a serial port is opened as a callout device. Of course, the HUPCL termios flag must be enabled if the hangup is to occur. __low_latency__ Minimize the receive latency of the serial device at the cost of greater CPU utilization. (Normally there is an average of 5-10ms latency before characters are handed off to the line discpline to minimize overhead.) This is off by default, but certain real-time applications may find this useful. __^low_latency__ Optimize for efficient CPU processing of serial characters at the cost of paying an average of 5-10ms of latency before the characters are processed. This is the default. !!CONSIDERATIONS OF CONFIGURING SERIAL PORTS It is important to note that setserial merely tells the Linux kernel where it should expect to find the I/O port and IRQ lines of a particular serial port. It does *not* configure the hardware, the actual serial board, to use a particular I/O port. In order to do that, you will need to physically program the serial board, usually by setting some jumpers or by switching some DIP switches. This section will provide some pointers in helping you decide how you would like to configure your serial ports. The /dev/ttyS0 (COM1), port 0x3f8, irq 4 /dev/ttyS1 (COM2), port 0x2f8, irq 3 /dev/ttyS2 (COM3), port 0x3e8, irq 4 /dev/ttyS3 (COM4), port 0x2e8, irq 3 Due to the limitations in the design of the AT/ISA bus architecture, normally an IRQ line may not be shared between two or more serial ports. If you attempt to do this, one or both serial ports will become unreliable if you try to use both simultaneously. This limitation can be overcome by special multi-port serial port boards, which are designed to share multiple serial ports over a single IRQ line. Multi-port serial cards supported by Linux include the AST !FourPort, the Accent Async board, the Usenet Serial II board, the Bocaboard BB-1004, BB-1008, and BB-2016 boards, and the HUB-6 serial board. The selection of an alternative IRQ line is difficult, since most of them are already used. The following table lists the IRQ 3: COM2 IRQ 4: COM1 IRQ 5: LPT2 IRQ 7: LPT1 Most people find that IRQ 5 is a good choice, assuming that there is only one parallel port active in the computer. Another good choice is IRQ 2 (aka IRQ 9); although this IRQ is sometimes used by network cards, and very rarely VGA cards will be configured to use IRQ 2 as a vertical retrace interrupt. If your VGA card is configured this way; try to disable it so you can reclaim that IRQ line for some other card. It's not necessary for Linux and most other Operating systems. The only other available IRQ lines are 3, 4, and 7, and these are probably used by the other serial and parallel ports. (If your serial card has a 16bit card edge connector, and supports higher interrupt numbers, then IRQ 10, 11, 12, and 15 are also available.) On AT class machines, IRQ 2 is seen as IRQ 9, and Linux will interpret it in this manner. IRQ's other than 2 (9), 3, 4, 5, 7, 10, 11, 12, and 15, should ''not'' be used, since they are assigned to other hardware and cannot, in general, be changed. Here are the '' IRQ 0 Timer channel 0 IRQ 1 Keyboard IRQ 2 Cascade for controller 2 IRQ 3 Serial port 2 IRQ 4 Serial port 1 IRQ 5 Parallel port 2 (Reserved in PS/2) IRQ 6 Floppy diskette IRQ 7 Parallel port 1 IRQ 8 Real-time clock IRQ 9 Redirected to IRQ2 IRQ 10 Reserved IRQ 11 Reserved IRQ 12 Reserved (Auxillary device in PS/2) IRQ 13 Math coprocessor IRQ 14 Hard disk controller IRQ 15 Reserved !!MULTIPORT CONFIGURATION Certain multiport serial boards which share multiple ports on a single IRQ use one or more ports to indicate whether or not there are any pending ports which need to be serviced. If your multiport board supports these ports, you should make use of them to avoid potential lockups if the interrupt gets lost. In order to set these ports specify __set_multiport__ as a parameter, and follow it with the multiport parameters. The multiport parameters take the form of specifying the ''port'' that should be checked, a ''mask'' which indicate which bits in the register are significant, and finally, a ''match'' parameter which specifies what the significant bits in that register must match when there is no more pending work to be done. Up to four such port/mask/match combinations may be specified. The first such combinations should be specified by setting the parameters __port1__, __mask1__, and __match1__. The second such combination should be specified with __port2__, __mask2__, and __match2__, and so on. In order to disable this multiport checking, set __port1__ to be zero. In order to view the current multiport settings, specify the parameter __get_multiport__ on the command line. Here are some multiport settings for some common serial boards: AST !FourPort port1 0x1BF mask1 0xf match1 0xf Boca BB-1004/8 port1 0x107 mask1 0xff match1 0 Boca BB-2016 port1 0x107 mask1 0xff match1 0 port2 0x147 mask2 0xff match2 0 !!Hayes ESP Configuration __Setserial__ may also be used to configure ports on a Hayes ESP serial board. The following parameters when configuring ESP ports: __rx_trigger__ This is the trigger level (in bytes) of the receive FIFO. Larger values may result in fewer interrupts and hence better performance; however, a value too high could result in data loss. Valid values are 1 through 1023. __tx_trigger__ This is the trigger level (in bytes) of the transmit FIFO. Larger values may result in fewer interrupts and hence better performance; however, a value too high could result in degraded transmit performance. Valid values are 1 through 1023. __flow_off__ This is the level (in bytes) at which the ESP port will __flow_on__ This is the level (in bytes) at which the ESP port will __rx_timeout__ This is the amount of time that the ESP port will wait after receiving the final character before signaling an interrupt. Valid values are 0 through 255. A value too high will increase latency, and a value too low will cause unnecessary interrupts. !!CAUTION CAUTION: Configuring a serial port to use an incorrect I/O port can lock up your machine. !!FILES __/etc/serial.conf /etc/init.d/setserial__ !!SEE ALSO tty(4), ttys(4), kernel/chr_drv/serial.c !!AUTHOR The original version of setserial was written by Rick Sladkey (jrs@world.std.com), and was modified by Michael K. Johnson (johnsonm@stolaf.edu). This version has since been rewritten from scratch by Theodore Ts'o (tytso@mit.edu) on 1/1/93. Any bugs or problems are solely his responsibility. Debian related problems with this system should be sent to Gordon Russell (gor@debian.org). ----
17 pages link to
setserial(8)
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Man8s
console_ioctls(4)
cfgetispeed(3)
cfgetospeed(3)
cfmakeraw(3)
cfsetispeed(3)
cfsetospeed(3)
cytune(8)
tcdrain(3)
tcflow(3)
tcflush(3)
tcgetattr(3)
tcgetpgrp(3)
tcsendbreak(3)
tcsetattr(3)
tcsetpgrp(3)
termios(3)
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