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Transfer of Subsystem Control Blocks and Termination Status Blocks between System and Subsystem by Registers

IP.com Disclosure Number: IPCOM000113568D
Original Publication Date: 1994-Sep-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 80K

Publishing Venue

IBM

Related People

Keener, D: AUTHOR [+3]

Abstract

Disclosed is the transfer of Subsystem Control Blocks (SCB) and Termination Status Blocks (TSB) of information between a system processor bus and a SCSI subsystem processor by means of registers which can be accessed by both the system and subsystem processors. This data is passed, a word or a byte at a time, between a register inside the SCSI controller and the system, so that the processor is not stuck in a hold state longer than the time required to pass a word or byte.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Transfer of Subsystem Control Blocks and Termination Status Blocks
between System and Subsystem by Registers

      Disclosed is the transfer of Subsystem Control Blocks (SCB) and
Termination Status Blocks (TSB) of information between a system
processor bus and a SCSI subsystem processor by means of registers
which can be accessed by both the system and subsystem processors.
This data is passed, a word or a byte at a time, between a register
inside the SCSI controller and the system, so that the processor is
not stuck in a hold state longer than the time required to pass a
word or byte.

      Between each word or byte, the SCSI controller allows the
system processor time to access the system bus to perform commands.
When the system processor has control of the system bus, the
subsystem processor is processing data in the SCSI controller
registers.  Thus, both processors can be working at the same time,
and the system bus is efficiently utilized.

      The HBV, LBV, SCB TRANSFER, and AUTO CLEAR signals, provided as
outputs of registers, are established as handshaking signals to allow
SCB and TSB data to pass between registers attached to the SCSI
controller, the system bus, and the subsystem processor.  The HBV and
LBV bits inform the subsystem processor that data for the high-byte
registers and for the low-byte registers, respectively, can either be
read or written, depending on the direction data is traveling, as
indicated by a direction bit.  The SCB TRANSFER bit is used to inform
the SCSI controller that the present transfer of data is using the
SCB registers, instead of a path to a SCSI device.  The AUTO CLEAR
bit is used to activate the ability to clear the HBV and LBV signals
when the SCB data registers are read by the subsystem processor.

      Data is transferred from the system to the subsystem when the
system informs the SCSI controller that an SCB request will be
coming.  The subsystem processor sets the direction bit, the SCB
TRANSFER bit,...