.\"
.\" Copyright (c) 1996 Jonathan Stone.
.\" All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
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.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"      This product includes software developed by Jonathan Stone.
.\" 3. The name of the author may not be used to endorse or promote products
.\"    derived from this software without specific prior written permission
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.\"	$OpenBSD: scc.4,v 1.4 2001/10/05 14:45:53 mpech Exp $
.\"
.Dd March 7, 1998
.Dt SCC 4 alpha
.Os
.Sh NAME
.Nm scc
.Nd Zilog serial communications interface
.Sh SYNOPSIS
.Cd "scc0 at ioasic? offset ?"
.Cd "scc1 at ioasic? offset ?"
.Sh DESCRIPTION
The
.Nm
driver provides support for the Zilog 8530 Serial Communications
Controller (SCC) via the IOCTL asic on Turbochannel-based alphas
(the DEC 3000 series).
Each scc device has two serial ports.
.Pp
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, or 57600.
Speeds up to 230400 are supported by the chip and the motherboard,
but speeds  higher than 57600 do not work reliably without an external
clock signal.
.Sh FILES
.Bl -tag -width Pa
.It Pa /dev/ttyB0
.It Pa /dev/ttyB1
.El
.Pp
The mapping from units to serial-hardware outlets is idiosyncratic.
.Sh HISTORY
The
.Nm
driver first appeared in
.Bx 4.4 .
.Sh BUGS
The IOCTL asic provides internal DMA channels that can be programmed
to transfer  up to 4096 bytes of data into, or out, of an SCC without
further software intervention.
This feature of the ioctl asic is not yet supported.
.Pp
The mapping from device-special files (major and minor number) to chip
and port is arguably backwards.