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@(#)tu.4 6.1 (Berkeley) 05/15/85

C 4 tu - VAX-11/730 and VAX-11/750 TU58 console cassette interface "options MRSP" (for VAX-11/750's with an MRSP prom) The tu interface provides access to the VAX 11/730 and 11/750 TU58 console cassette drive(s).

The interface supports only block i/o to the TU58 cassettes. The devices are normally manipulated with the arff (8V) program using the ``f'' and ``m'' options.

The device driver is automatically included when a system is configured to run on an 11/730 or 11/750.

The TU58 on an 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. On an 11/730 the Modified Radial Serial Protocol is used. This protocol incorporates flow control measures which insure reliable data transfer between the cpu and the device. Certain 11/750's have been modified to use the MRSP prom used in the 11/730. To reliably use the console TU58 on an 11/750 under UNIX, the MRSP prom is required. For those 11/750's without an MRSP prom, an unreliable but often useable 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 an 11/730 or use an MRSP prom. This unfortunately makes it impossible to configure a single system which will properly handle TU58's on both an 11/750 and an 11/730 (unless both machines have MRSP proms).

/dev/tu0
/dev/tu1 (only on a VAX-11/730)

arff(8V) "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 (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.

The VAX-11/750 console interface without MRSP prom is unuseable while the system is multi-user; it should be used only with the system running single-user and, even then, with caution.