ZS(4S) — SPECIAL FILES

NAME

zs − zilog 8530 SCC serial comunications driver

SYNOPSIS

device zs0 at mb0 csr 0xf5a000 flags 3 priority 6

DESCRIPTION

The Zilog 8530 provides 2 serial communication lines with full modem control. Each line behaves as described in tty(4). Input and output for each line may independently be set to run at any of 16 speeds; see tty(4) for the encoding.

Bit i of flags may be specified to say that a line is not properly connected, and that the line i should be treated as hard-wired with carrier always present. Thus specifying “flags 0x2” in the specification of zs0 would cause line ttyb to be treated in this way.

To allow a single tty line to be connected to a modem and used for both incoming and outgoing calls, a special feature, controlled by the minor device number, has been added. Minor device numbers in the range 0 − 127 correspond directly to the normal tty lines and are named tty∗. Minor device numbers in the range 128 − 256 correspond to the same physical lines as those above (i.e. the same line as the minor device number minus 128) and are (conventionally) named cua∗. The cua lines are special in that they can be opened even when there is no carrier on the line. Once a cua line is opened, the corresponding tty line can not be opened until the cua line is closed. Also, if the tty line has been opened successfully (usually only when carrier is recognized on the modem) the corresponding cua line can not be opened. This allows a modem to be attached to /dev/ttya (usually renamed to /dev/ttyd0) and used for dialin (by enabling the line for login in /etc/ttys) and also used for dialout (by tip(1C) or uucp(1C)) as /dev/cua0 when no one is logged in on the line. Note that the bit in the flags word in the config file (see above) must be zero for this line.

FILES

/dev/tty[a,b,s0-s3]
/dev/ttyd[0-9,a-f]
/dev/cua[0-9,a-f]

DIAGNOSTICS

zs%d%c: silo overflow. The character input silo overflowed before it could be serviced.

Sun Release 1.4 — Last change: 21 August 1984

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