ctu(4)									ctu(4)

Name
       ctu - TU58 console interface

Syntax
       options MRSP (for VAX-11/750's with an MRSP prom)

Description
       Prior to Version 2.0, this device was referenced using

       The interface provides access to the VAX-11/730 (11/725) and VAX-11/750
       TU58 console cassette drive.

       The interface supports only block  I/O  to  the	TU58  cassettes.   The
       devices	are  normally  manipulated  with  the  program,	 using the and
       options.

       The device driver is automatically included when a system is configured
       to run on a VAX-11/730 (11/725) or VAX-11/750.

       The  TU58 on a VAX-11/750 uses the Radial Serial Protocol (RSP) to com‐
       municate with the CPU over a serial line.  This protocol is  inherently
       unreliable  as  it  has	no  flow  control  measures  built  in.	  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 unre‐
       liable 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  sys‐
       tem,  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).

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.

Diagnostics
       tu%d: no bp, active %d
       A  transmission complete interrupt was received with no outstanding I/O
       request.	 This indicates a hardware problem.

       tu%d protocol error, state=%s, op=%x, cnt=%d, block=%d
       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.

       tu%d receive state error, state=%s, byte=%x
       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.

       tu%d: read stalled
       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).

       tu%d: hard error bn%d, pk_mod %o
       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.

Files
       (only on a VAX-11/730 (11/725))

See Also
       MAKEDEV(8)

				      VAX				ctu(4)

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