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A device that presents a USB Mass Storage device as a Direct Access device to a SCSI controller.
A device that presents a USB Mass Storage device as a Direct Access device to a SCSI controller.
== Specifications ==
* Fast Narrow Single-Ended SCSI-2


== Why ? ==
== Why ? ==
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* (Check) 3.3v to 5v level converter ?
* (Check) 3.3v to 5v level converter ?
* [http://au.element14.com/texas-instruments/cd74ac280e/logic-parity-gen-chker-9bit-14dip/dp/1753467 TI CD74AC280E]/74HC280 Parity checker/generator.
* [http://au.element14.com/texas-instruments/cd74ac280e/logic-parity-gen-chker-9bit-14dip/dp/1753467 TI CD74AC280E]/74HC280 Parity checker/generator.
== SCSI Electrical Interface ==
SE and LVD devices may co-exist on a SCSI chain, but the chain will be reduced to SE functionality.
=== Single Ended (SE) ===
* Still supported on new U320 drives.
* TTL logic levels.
* Up to 40MB/sec (Ultra Wide SCSI).
=== Low-voltage differential (LVD) ===
* [http://en.wikipedia.org/wiki/RS-485 RS-485] compatible.  Either LVD SCSI Transceivers or RS-485 transceivers may be used.
* Up to 320MB/sec (Ultra-320 SCSI).


== Links ==
== Links ==

Revision as of 09:31, 28 September 2011

A device that presents a USB Mass Storage device as a Direct Access device to a SCSI controller.

Specifications

  • Fast Narrow Single-Ended SCSI-2

Why ?

Because there are many vintage computers out there that require a 50-pin SCSI drive to boot from. Such disks are only available second-hand, and it's getting harder and harder to find a working disk.

Alternatives

  • The price of commercial SCSI converters can be much higher than the vintage computers they are used in. However, these devices are still readily available.
  • 50pin to 68pin or 80pin SCSI converters allow the use of newer drives. Availability of new SCSI SCA (80 pin) drives is limited to prohibitively expensive 15K RPM "enterprise" drives.

Why USB ?

Because USB Mass Storage devices already understand SCSI commands.

Parts Required

  • SCSI Terminator. TI UC5601DWPG4
  • AT90USB1286
  • 50 pin IDC header
  • USB socket
  • 5V supply via Molex drive connector
  • (Check) 3.3v to 5v level converter ?
  • TI CD74AC280E/74HC280 Parity checker/generator.

SCSI Electrical Interface

SE and LVD devices may co-exist on a SCSI chain, but the chain will be reduced to SE functionality.

Single Ended (SE)

  • Still supported on new U320 drives.
  • TTL logic levels.
  • Up to 40MB/sec (Ultra Wide SCSI).

Low-voltage differential (LVD)

  • RS-485 compatible. Either LVD SCSI Transceivers or RS-485 transceivers may be used.
  • Up to 320MB/sec (Ultra-320 SCSI).

Links

The following projects will be of great help:

Reference information: