.\"	$NetBSD: tu.4,v 1.16 2009/04/11 22:21:44 wiz Exp $
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.\"     from: @(#)tu.4	8.1 (Berkeley) 6/5/93
.\"
.Dd June 5, 1993
.Dt TU 4 vax
.Os
.Sh NAME
.Nm tu
.Nd
.Tn VAX-11/750
.Tn TU-58
console cassette interface
.Sh DESCRIPTION
The
.Nm tu
interface provides access to the
.Tn VAX-11/750
.Tn TU-58
console cassette drive.
.Pp
The interface supports only block
.Tn I/O
to the
.Tn TU-58
cassettes.
The devices are normally manipulated with the
.Xr dd 1
program.
.Pp
The device driver is automatically included when a
system is configured to run on an 11/750.
.Pp
The
.Tn TU-58
on an 11/750 uses the Radial Serial Protocol
.Pq Tn RSP
to communicate with the cpu over a serial line.
This protocol is inherently unreliable as it has no flow
control measures built in.
.Sh FILES
.Bl -tag -width /dev/tu0xx -compact
.It Pa /dev/tu0
.El
.Sh DIAGNOSTICS
.Bl -diag
.It tu%d: lost recv interrupt.
A timer watching the controller detected no interrupt for
an extended period while an operation was outstanding.
This usually indicates that one or more receiver interrupts
were lost and the transfer is restarted.
.El
.Sh HISTORY
The
.Nm
driver appeared in
.Bx 4.1 .
.br
A new driver showed up in
.Nx 1.2 .
.Sh BUGS
The
.Tn VAX-11/750
console interface is unusable
while the system is multi-user, because interrupts
occur at a very high priority level (spl7) and cannot be blocked with splbio.
Use this driver only when the system is running single-user and,
even then, with caution.