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Browse Prior Art Database

SCSI Transfer Control Circuit

IP.com Disclosure Number: IPCOM000109806D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 3 page(s) / 75K

Publishing Venue

IBM

Related People

Iwasa, H: AUTHOR [+3]

Abstract

Disclosed is a SCSI transfer rate control circuit for a HDD (Hard Disk Drive). This circuit can easily control the SCSI transfer rate from fast SCSI mode (up to 10MB/s) to normal SCSI mode (under 5MB/s).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 59% of the total text.

SCSI Transfer Control Circuit

       Disclosed is a SCSI transfer rate control circuit for a
HDD (Hard Disk Drive).  This circuit can easily control the SCSI
transfer rate from fast SCSI mode (up to 10MB/s) to normal SCSI mode
(under 5MB/s).

      The characteristics of this invention are as follows: It has an
N-bit register to decide the transfer rate.  The Nth bit (most
significant bit) of the N-bit register is used as clock select bit
which decides whether the clock is divided or not.  This clock is
used to control the SCSI -REQ signal pulse width.  The N-1 bits
except the Nth bit are used to control the number of wait cycles to
extend the SCSI -REQ signal.

      Fig. 1 shows the circuit block diagram of this invention.  The
outputs of the N-bit transfer control register 1 are connected to the
clock-divider and selector 2 and wait number counter 3.  STCLK is the
same frequency as the source CLOCK when the input from register 1 is
0.  When the input from register 1 is 1, then STCLK is 1/2 the
frequency of CLOCK.  Wait number counter 3 counts the number of
clocks to develop the wait cycle of -REQ signal. The value of wait is
set by register 1.  State machine 4 develops the SCSI -REQ signal. If
the WAIT ON signal is active, then the high level of the SCSI -REQ
signal is expanded. And if STCLK is 1/2 the frequency of CLOCK, then
the SCSI -REQ signal's low/high width is twice that of the original.

      Fig. 2 shows the example of the waveform. ...