Copyright (c) 1980 Regents of the University of California.
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@(#)dz.4 6.1 (Berkeley) 05/15/85

C 4 dz - DZ-11 communications multiplexer "device dz0 at uba0 csr 0160100 vector dzrint dzxint" A dz-11 provides 8 communication lines with partial modem control, adequate for UNIX dialup use. Each line attached to the DZ-11 communications multiplexer behaves as described in tty (4) and may be set to run at any of 16 speeds; see tty (4) for the encoding.

Bit i of flags may be specified for a dz to say that a line is not properly connected, and that the line should be treated as hard-wired with carrier always present. Thus specifying ``flags 0x04'' in the specification of dz0 would cause line tty02 to be treated in this way.

The dz driver normally uses its input silos and polls for input at each clock tick (10 milliseconds) rather than taking an interrupt on each input character.

/dev/tty[0-9][0-9]

/dev/ttyd[0-9a-f] dialups

tty(4)

dz%d: silo overflow. The 64 character input silo overflowed before it could be serviced. This can happen if a hard error occurs when the CPU is running with elevated priority, as the system will then print a message on the console with interrupts disabled. If the Berknet is running on a dz line at high speed (e.g. 9600 baud), there is only 1/15th of a second of buffering capacity in the silo, and overrun is possible. This may cause a few input characters to be lost to users and a network packet is likely to be corrupted, but the network will recover. It is not serious.