NetBSD/share/man/man4/man4.pmax/scc.4

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.\"	$NetBSD: scc.4,v 1.6 1999/04/06 20:24:50 pk Exp $
.\"
.Dd August 6, 1996
.Dt SCC 4 pmax
.Os
.Sh NAME
.Nm scc
.Nd
Zilog 8530 Serial Communications Controller interface
.Sh SYNOPSIS
.Cd "scc0 at ioasic?"
.Cd "scc1 at ioasic?"
.Sh DESCRIPTION
The
.Nm
driver provies support for the Zilog 8530 Serial Communcations
Controller (SCC) via the IOCTL ASIC on DECstation 5000 models
in the /100, /20, and /240 series.
Each SCC device has two serial ports.
The model 20 provides one SCC device.
Other models provide two, but one port of each device is dedicated
to mouse and keyboard input, respectively.
.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/ttya
.It Pa /dev/ttyb
.It Pa /dev/ttyc
.It Pa /dev/ttyd
.El
.Pp
The mapping from units to serial-hardware outlets is idiosyncratic.
The even ports are wired serial connectors and the odd-numbered ports
are reserved for mouse and keyboard.
On machines with one port like
.Tn "Personal DECstations" ,
the single device is
.Pa ttya .
On the 
.Tn "5000/1xx" 
and
.Tn "5000/2xx" ,
the first serial port (default serial console) is
.Pa ttyc
and the second port is 
.Pa ttya .
.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.
.Tn Ultrix
tries to hide the hardware mapping, but
.Nx
does not.
Users wanting to use
.Tn "Ultrix"
compatible tty names 
.Pa /dev/tty0
and
.Pa /dev/tty1
for the
.Nm
comm-port lines should make links or device-special files which match
their hardware setup.