Browse Prior Art Database

Direct Access Storage Device (DASD) Concurrent Maintenance

IP.com Disclosure Number: IPCOM000119295D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 5 page(s) / 172K

Publishing Venue

IBM

Related People

Dimmick, RF: AUTHOR [+3]

Abstract

Disclosed is a device for performing concurrent maintenance on a direct access storage device (DASD) or save/restore device, such as a tape drive, while the system continues to operate. When a system package contains multiple devices, it should be possible to perform concurrent maintenance upon any one of those devices while the remainder of those devices continues to operate. To achieve concurrent maintenance, it must be possible to: 1) protect the connectors from arcing which destroys the contacts, 2) prevent latch-up of drivers and receivers on plugged cards, 3) prevent inrush current from stressing the power system, and 4) prevent errors from propagating into the remainder of the system which must be capable of continuing operation. The following describes how the above four items are accomplished.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 42% of the total text.

Direct Access Storage Device (DASD) Concurrent Maintenance

      Disclosed is a device for performing concurrent
maintenance on a direct access storage device (DASD) or save/restore
device, such as a tape drive, while the system continues to operate.
When a system package contains multiple devices, it should be
possible to perform concurrent maintenance upon any one of those
devices while the remainder of those devices continues to operate.
To achieve concurrent maintenance, it must be possible to:  1)
protect the connectors from arcing which destroys the contacts, 2)
prevent latch-up of drivers and receivers on plugged cards, 3)
prevent inrush current from stressing the power system, and 4)
prevent errors from propagating into the remainder of the system
which must be capable of continuing operation.  The following
describes how the above four items are accomplished.

      In the implementation to be described, the number of mating
connections is again too large for an edge connector, and the
tolerances of the docking system do not allow the order of the mating
connections to be guaranteed.  The connectors used are pin-in-socket
connectors for the power input in a tray, and the architected SCSI
connectors described in ANSI X3T9/89-042, or the 96-Pin DIN
pin-in-socket connector for the book implementation.

      Within the context of the above paragraph, this invention's
features are:
      -    The contacts of the connectors are protected by removal of
all voltage and signal power during the plugging and unplugging of
the books or trays.
      -    Latch-up is prevented by removal of power from both the
drivers and receivers on the interface bus, independent of whether
the card is already present on the bus or whether the card is being
plugged on the bus.
      -    Glitch interference with the operating devices is provided
by:  1) separate buses for each device, 2) removal of power from the
interface drivers and receivers, and by 3) an inrush current
management circuit.
      -    The inrush current management circuit also prevents the
bulk supply from seeing an over-current situation when the interlock
switch which protects the power connector is closed.
      -    The inrush current management circuit is switched out to
allow adequate current capability from the bulk supply for operation
of the device after the device and regulator capacitances have
reached a stable charge state.  Two separate and distinct
implementations of the terminator power interface for the SCSI bus
will be described.  Fig. 1 shows the implementation for the
multi-dropped bus used with M2 and the CEC which contain the DASD
book package and the save/restore tray implementations. Fig. 2 shows
the implementation of the terminator power interface for the single
drop SCSI bus device interface in the multimedia (M1) box.  The
removal of terminator power protects the signal connector from
material erosion during...