Browse Prior Art Database

Programmable Small Computer System Interface Terminator Power

IP.com Disclosure Number: IPCOM000116776D
Original Publication Date: 1995-Nov-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Karp, JM: AUTHOR [+2]

Abstract

A method for providing terminator power as an optional feature programmed from the operator panel is described. This allows term power to be enabled/disabled without access to the internal circuit cards.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 61% of the total text.

Programmable Small Computer System Interface Terminator Power

      A method for providing terminator power as an optional feature
programmed from the operator panel is described.  This allows term
power
to be enabled/disabled without access to the internal circuit cards.

      Small Computer System Interface (SCSI) require termination and
terminator power to operate properly.  However, for targets (drives)
these functions must be optional.  This method provides terminator
power as a programmable feature that the user may select from the
operator panel.  Once selected, the setting is stored in non-volatile
FEPROM and restored after power cycles.  Additional circuits are
added to allow microcode to control the sourcing of terminator power
from a register bit that may be read/written from the code.
Additionally, terminators may be prograamed in the same manner.

      The Figure is a block diagram of the solution.  The user
selects the option on the operator panel.  Microcode stores the
setting in FEPROM and also updates the register control bit to the
proper value.  If term power is selected, the P-Channel FET is turned
on allowing termpower to be sourced through diode D1 and fuse F1.  If
not selected, the FET is off and no current will flow.

      At subsequent Power On or Reset, the control register is
initially three-stated then set by hardware which forces termpower
off until POD diagnostics are complete and good machine operation is
assured. ...