Fujitsu M2488 manual Operation of the Magnetic Tape Unit MTU, Firmware, Airless Tape Path

DESIGN ARCHITECTURE M2488 PRODUCT GUIDE

2-3.5 Firmware

The M2488 microcode is partitioned into functional modules and stored in mask ROM and flash memory. The code partitions serve to minimize communication paths within the code structure and to segregate functions dealing with the host interface from those dealing with generic tape operation. The mask ROM provides a resident code version for power-on and code download. New code ver- sions are downloaded into flash memory from the host SCSI interface or from tape. After power-on, control store for all processors is loaded from flash memory if valid. If invalid, the mask ROM code is used for recovery.

The core microcode is a multi-tasking operating system (OS) allowing a configurable number of tasks. The present design allows a total of thirty two active tasks; four fixed tasks and twenty-eight SCSI tasks. This custom OS allows functions to run until a resource is unavailable, places itself into a suspended state until the resource becomes available, and then proceeds with execution. Many over- lapped operations are possible because of a sophisticated interrupt structure. Servo, formatter, main- tenance, and SCSI events are signalled via interrupts which in turn initiate processes via the OS to service the events. Signals generated from the read detection circuitry are given highest priority by polling them with the read signal verification processor (RSVP) embedded in the PCC LSI.

2-4 OPERATION OF THE MAGNETIC TAPE UNIT (MTU)

The magnetic tape unit consists of the read and write head, all mechanical assemblies (loader assembly, threader assembly, and servo motors), and five printed circuit assemblies that perform the following functions:

1)DVL PCA - control processor and logic for all servo and mechanical control functions. and oper- ator panel control processor. A logical block diagram for the DVL is shown in Figure 2-3. The interface and control logic is integrated into the MMCL LSI (denoted by the dotted line in the block diagram).

2)OP PCA - contains the M2488 unit operator panel and associated drive circuitry

3)SVL PCA - contains servo control circuitry including I/O registers, control logic LSI, PWM con- trol, and control DAC.

4)WTL PCA - contains the write drive circuits.

5)RDL PCA - contains the read analog circuits.

Other features of the MTU are described in the following sections.

2-4.1 Airless Tape Path

The M2488 has been able to realize an airless tape path while maintaining excellent reliability. This system removes the failure-prone pump and pack arm assemblies with an improved roller guide tape path. One new roller guide has been added that replaces the pack arm to keep tape aligned with the tape machine reel. Alignment of tape with the head is accomplished with two roller guides as in pre- vious models. During running, a slight air film is produced between the head and tape which prevents direct contact. A patrol reposition function has been added that periodically moves the tape to prevent any problem when tape is not moving.

The reel motor of the M2488 has also been changed to dramatically improve tape reposition time and access times.

2-4 CG00000-011503 REV. A April 1997