ctu.4

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)ctu.4	8.1	9/11/90
.\" SCCSID: @(#)ctu.4	8.1	9/11/90
.TH ctu 4 VAX
.SH Name
ctu \- TU58 console interface
.SH Syntax
.B "options MRSP"
(for VAX-11/750's with an MRSP prom)
.SH Description
.NXR "ctu keyword"
.NXR "TU58 console interface"
Prior to Version 2.0, this device was referenced using
.PN tu(4) .
.PP
The
.PN ctu
interface provides access to the VAX-11/730 (11/725) 
and VAX-11/750 TU58 console cassette drive.
.PP
The interface supports only block I/O to the TU58 cassettes.
The devices are normally manipulated with the
.MS arff 8v
program, using the 
.PN f 
and 
.PN m
options.
.PP
The device driver is automatically included when a
system is configured to run on a VAX-11/730 (11/725) or VAX-11/750.
.PP
The TU58 on a VAX-11/750 uses the Radial Serial Protocol (RSP)
to communicate with the CPU over a serial line.  This
protocol is inherently unreliable as it has no flow
control measures built in.  
.NXR "RSP" "VAX-11/750 and"
.NXS "Radial Serial Protocol" "RSP"
On a VAX-11/730 (11/725), the Modified
Radial Serial Protocol is used.  This protocol incorporates
flow control measures that ensure reliable data transfer
between the CPU and the device.  Certain VAX-11/750s have
been modified to use the MRSP prom used in the VAX-11/730 (11/725).
To reliably use the console TU58 on an VAX-11/750 under ULTRIX,
the MRSP prom is required.  For those VAX-11/750s without
an MRSP prom, an unreliable but often
usable interface has been developed.
This interface uses an assembly language ``pseudo-dma'' routine
to minimize the receiver interrupt service latency.
To include this code in
the system, the configuration must not specify the
system will run on a VAX-11/730 (11/725) or use an MRSP prom.
This unfortunately makes it impossible to configure a
single system that will properly handle TU58s on both a VAX-11/750
and an VAX-11/730 (11/725) (unless both machines have MRSP proms).
.SH Restrictions
Frequent data overruns can occur if the VAX-11/750 TU58 is used
while in multiuser mode. The interface continues to function
and errors are handled, but transfer times may be lengthened
considerably.
.SH Diagnostics
.B "tu%d: no bp, active %d" 
.br
A transmission complete interrupt was received with no outstanding
I/O request.  This indicates a hardware problem.
.PP
.B "tu%d protocol error, state=%s, op=%x, cnt=%d, block=%d"
.br
The driver entered an illegal state.  The information printed
indicates the illegal state, operation currently being executed,
the I/O count, and the block number on the cassette.
.PP
.B "tu%d receive state error, state=%s, byte=%x"
.br
The driver entered an illegal state in the receiver finite
state machine.	The state is shown along with the control
byte of the received packet.
.PP
.B "tu%d: read stalled"
.br
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 (VAX-11/750 only).
.PP
.B "tu%d: hard error bn%d, pk_mod %o"
.br
The device returned a status code indicating a hard error. The
actual error code is shown in octal. No retries are attempted
by the driver.
.SH Files
.TP 15
.PN /dev/tu0

.TP
.PN /dev/tu1
(only on a VAX-11/730 (11/725))
.SH See Also
MAKEDEV(8)