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 tu(4).
The ctu interface provides access to the VAX-11/730 (11/725) 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() program using the “f” and “m” options.
The device driver is automatically included when a system is configured to run on a VAX-11/730 (11/725) 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 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 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 11/750 under ULTRIX, the MRSP prom is required. For those 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).
RESTRICTIONS
Frequent data overruns may occur if the VAX-11/750 TU58 is used while in multiuser mode. The interface will continue to function and errors will be 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
/dev/tu0
/dev/tu1(only on a VAX-11/730 (11/725))