DIGI(4) BSD Kernel Interfaces Manual DIGI(4)NAMEdigi — DigiBoard intelligent serial cards driver
This man page was originally written for the dgb driver, and should
likely be gone over with a fine tooth comb to reflect differences with
the digi driver.
When not defined the number is computed:
default NDGBPORTS = number_of_described_DigiBoard_cards * 16
If it is less than the actual number of ports the system will be able to
use only the first NDGBPORTS ports. If it is greater then all ports will
be usable but some memory will be wasted.
Meaning of flags:
0x0001 use alternate pinout (exchange DCD and DSR lines)
0x0002 do not use 8K window mode of PC/Xe
The digi driver provides support for DigiBoard PC/Xe and PC/Xi series
intelligent serial multiport cards with asynchronous interfaces based on
the EIA RS-232C (CCITT V.24) standard.
Input and output for each line may set to one of following baud rates;
50, 75, 110, 134.5, 150, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200,
38400, 57600, or for newer versions of cards 115200.
The driver does not use any interrupts, it is “polling-based”. This
means that it uses clock interrupts instead of interrupts generated by
DigiBoard cards and checks the state of cards 25 times per second. This
is practical because the DigiBoard cards have large input and output buf‐
fers (more than 1Kbyte per port) and hardware that allows efficiently
finding the port that needs attention. The only problem seen with this
policy is slower SLIP and PPP response.
Each line in the kernel configuration file describes one card, not one
port as in the sio(4) driver.
The flags keyword may be used on each “device dgb” line in the kernel
configuration file to change the pinout of the interface or to use new
PC/Xe cards which can work with an 8K memory window in compatibility mode
(with a 64K memory window). Note that using 8K memory window does not
mean shorter input/output buffers, it means only that all buffers will be
mapped to the same memory address and switched as needed.
The port value must be the same as the port set on the card by jumpers.
For PC/Xi cards the same rule is applicable to the iomem value. It must
be the same as the memory address set on the card by jumpers. For PC/Xe
cards there is no need to use jumpers for this purpose. In fact there
are no jumpers to do it. Just write the address you want as the iomem
value in kernel config file and the card will be programmed to use this
The same range of memory addresses may be used for all the DigiBoards
installed (but not for any other card or real memory). DigiBoards with a
large amount of memory (256K or 512K and perhaps even 128K) must be
mapped to memory addresses outside of the first megabyte. If the com‐
puter has more than 15 megabytes of memory then there is no free address
space outside of the first megabyte where such DigiBoards can be mapped.
In this case you may need to reduce the amount of memory in the computer.
But many machines provide a better solution. They have the ability to
“turn off” the memory in the 16th megabyte (addresses 0xF00000 -
0xFFFFFF) using the BIOS setup. Then the DigiBoard's address space can
be set to this “hole”.
Serial ports controlled by the digi driver can be used for both “callin”
and “callout”. For each port there is a callin device and a callout
device. The minor number of the callout device is 128 higher than that
of the corresponding callin port. The callin device is general purpose.
Processes opening it normally wait for carrier and for the callout device
to become inactive. The callout device is used to steal the port from
processes waiting for carrier on the callin device. Processes opening it
do not wait for carrier and put any processes waiting for carrier on the
callin device into a deeper sleep so that they do not conflict with the
callout session. The callout device is abused for handling programs that
are supposed to work on general ports and need to open the port without
waiting but are too stupid to do so.
The digi driver also supports an initial-state and a lock-state control
device for each of the callin and the callout “data” devices. The minor
number of the initial-state device is 32 higher than that of the corre‐
sponding data device. The minor number of the lock-state device is 64
higher than that of the corresponding data device. The termios settings
of a data device are copied from those of the corresponding initial-state
device on first opens and are not inherited from previous opens. Use
stty(1) in the normal way on the initial-state devices to program initial
termios states suitable for your setup.
The lock termios state acts as flags to disable changing the termios
state. E.g., to lock a flag variable such as CRTSCTS, use “stty crtscts”
on the lock-state device. Speeds and special characters may be locked by
setting the corresponding value in the lock-state device to any nonzero
Correct programs talking to correctly wired external devices work with
almost arbitrary initial states and no locking, but other setups may ben‐
efit from changing some of the default initial state and locking the
state. In particular, the initial states for non (POSIX) standard flags
should be set to suit the devices attached and may need to be locked to
prevent buggy programs from changing them. E.g., CRTSCTS should be
locked on for devices that support RTS/CTS handshaking at all times and
off for devices that do not support it at all. CLOCAL should be locked
on for devices that do not support carrier. HUPCL may be locked off if
you do not want to hang up for some reason. In general, very bad things
happen if something is locked to the wrong state, and things should not
be locked for devices that support more than one setting. The CLOCAL
flag on callin ports should be locked off for logins to avoid certain
security holes, but this needs to be done by getty if the callin port is
used for anything else.
/dev/ttyD?? for callin ports
/dev/ttylD?? corresponding callin initial-state and lock-state devices
/dev/cuaD?? for callout ports
/dev/cualD?? corresponding callout initial-state and lock-state devices
/etc/rc.serial examples of setting the initial-state and lock-state
The first question mark in these device names is short for the card num‐
ber (a decimal number between 0 and 65535 inclusive). The second ques‐
tion mark is short for the port number (a letter in the range [0-9a-v]).
You may enable extended diagnostics by defining DEBUG at the start of the
source file dgb.c.
dgbX: warning: address N truncated to M The memory address for the
PC/Xe's 8K window is misaligned (it should be on an 8K boundary) or out‐
side of the first megabyte.
dgbX: 1st reset failed Problems with accessing I/O port of the card,
probably the wrong port value is specified in the kernel config file.
dgbX: 2nd reset failed Problems with hardware.
dgbX: N[st,nd,rd,th] memory test failed Problems with accessing the mem‐
ory of the card, probably the wrong iomem value is specified in the ker‐
nel config file.
dgbX: BIOS start failed Problems with starting the on-board BIOS. Prob‐
ably the memory addresses of the DigiBoard overlap with some other device
or with RAM.
dgbX: BIOS download failed Problems with the on-board BIOS. Probably
the memory addresses of the DigiBoard overlap with some other device or
dgbX: FEP code download failed Problems with downloading of the Front-
End Processor's micro-OS. Probably the memory addresses of the DigiBoard
overlap with some other device or with RAM.
dgbX: FEP/OS start failed Problems with starting of the Front-End Pro‐
cessor's micro-OS. Probably the memory addresses of the DigiBoard over‐
lap with some other device or with RAM.
dgbX: too many ports This DigiBoard reports that it has more than 32
ports. Perhaps a hardware problem or the memory addresses of the Digi‐
Board overlap with some other device or with RAM.
dgbX: only N ports are usable The NDGBPORTS parameter is too small and
there is only enough space allocated for N ports on this card.
dgbX: port Y is broken The on-board diagnostic has reported that the
specified port has hardware problems.
dgbX: polling of disabled board stopped Internal problems in the polling
logic of driver.
dgbX: event queue's head or tail is wrong! Internal problems in the
driver or hardware.
dgbX: port Y: got event on nonexisting port Some status changed on a
port that is physically present but is unusable due to misconfiguration.
dgbX: port Y: event N mstat M lstat K The driver got a strange event
from card. Probably this means that you have a newer card with an
extended list of events or some other hardware problem.
dgbX: port Y: overrun Input buffer has filled up. Problems in polling
logic of driver.
dgbX: port Y: FEP command on disabled port Internal problems in driver.
dgbX: port Y: timeout on FEP command Problems in hardware.
SEE ALSOstty(1), termios(4), tty(4), comcontrol(8)HISTORY
The digi driver is derived from the sio(4) driver and the DigiBoard
driver from Linux and is currently under development.
The implementation of sending BREAK is broken. BREAK of fixed length of
1/4 s is sent anyway.
There was a bug in implementation of select(2). It is fixed now but not
widely tested yet.
There is no ditty command. Most of its functions (alternate pinout,
speed up to 115200 baud, etc.) are implemented in the driver itself.
Some other functions are missing.
BSD December 7, 2003 BSD