.\"	$NetBSD: zstty.4,v 1.3 1999/03/16 01:19:19 garbled Exp $
.\"
.\" Copyright (c) 1997 The NetBSD Foundation, Inc.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Gordon W. Ross.
.\"
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.Dd October 23, 1997
.Dt ZSTTY 4
.Os
.Sh NAME
.Nm zstty
.Nd
serial communications interface
.Sh SYNOPSIS
.Cd "zstty* at zs0"  Pq sparc
.Cd "zstty* at zsc1" Pq others
.Sh DESCRIPTION
The
.Nm
driver provides TTY support for Zilog 8530 Dual UARTS.
.Pp
Input and output for each line may set to any baud rate in the
range 50 to 38400 (and higher on some machines).
.Sh FILES
.Bl -tag -width Pa
.It Pa /dev/ttya
.It Pa /dev/ttyb
.El
.Sh DIAGNOSTICS
.Bl -tag -width indent -compact
.It zs0*: fifo overflow
.br
The on-chip
.Dq fifo
has overflowed and incoming data has been lost.
This generally means the machine is not responding to
interrupts from the ZS chip fast enough, which can be
remedied only by using a lower baud rate.
.It zs0*: ring overflow
.br
The software input
.Dq ring
has overflowed.  This usually means input flow-control
is not configured correctly (i.e. incorrect cable wiring).
.El
.Sh SEE ALSO
.Xr scc 4
.Xr tty 4
.Sh HISTORY
The
.Nm
driver was derived from the
.Nm sparc
.Nm zs
driver supplied with
.Bx 4.4 .
.Ud
.Sh BUGS
The old Zilog 8530 chip has a very small fifo (3 bytes?) and
therefore has very strict latency requirements for the
interrupt service routine.  This limits the usable baud rates
on many machines.