Seagate ST318405LW/LC manual Low voltage differential I/O circuits, General cable characteristics

Page 81

Cheetah 36XL Product Manual, Rev. E

71

9.7.1.1Single-ended drivers/receivers

The maximum total cable length allowed with drives using single-ended I/O driver and receiver circuits depends on several factors. Table 17 lists the maximum lengths allowed for different configurations of drive usage. These values are from the SPI-3 document. All device I/O lines must have equal to or less than 25 pf capacitance to ground, measured at the beginning of the stub.

Table 17: Cable characteristics for single-ended circuits

 

Maximum number of

Maximum cable

Transmission line impedance

 

 

 

I/O transfer rate

devices on the bus

length allowed

REQ/ACK

Other signals

 

 

 

 

 

 

 

 

 

 

<10M transfers/s

16 (wide SCSI bus)

6 meters (19.7 ft)

90 + 6 Ohms

90 + 10 Ohms

 

 

 

 

 

<20M transfers/s

4 (wide SCSI bus)

3 meters (9.8 ft)

90 + 6 Ohms

90 + 10 Ohms

 

 

 

 

 

<20M transfers/s

8 (wide SCSI bus)

1.5 meters (4.9 ft)

90 + 6 Ohms

90 + 10 Ohms

 

 

 

 

 

A stub length of no more than 0.1 meter (0.33 ft) is allowed off the mainline interconnection with any connected equipment. The stub length is measured from the transceiver to the connection to the mainline SCSI bus.

Single-ended I/O cable pin assignments for LW drives are shown in Table 14.

Single-ended I/O pin assignments for the LC models are shown in Table 15. The LC models do not require an I/O cable. They are designed to connect directly to a back panel connector.

9.7.1.2Low voltage differential I/O circuits

The maximum total cable length for use with drives using LVD I/O drivers and receiver circuits is 12 meters (39.37 ft.). A stub length of no more than 0.1 meter is allowed off the mainline interconnection with any con- nected equipment. LVD I/O pin assignments for LW model drives are shown in tables 13 and 14. LVD I/O pin assignments for LC model drives are shown in tables 15 and 16.

9.7.1.3General cable characteristics

A characteristic impedance of 100 ohm + 10% is recommended for unshielded flat or twisted pair ribbon cable. However, most available cables have a somewhat lower characteristic impedance. To Minimize discontinuities and signal reflections, cables of different impedances should not be used in the same bus. Implementations may require trade-offs in shielding effectiveness, cable length, the number of loads, transfer rates, and cost to achieve satisfactory system operation. If shielded and unshielded cables are mixed within the same SCSI bus, the effect of impedance mismatch must be carefully considered. Proper impedance matching is especially important in order to maintain adequate margin at fast SCSI transfer rates.

9.8Terminator requirements

Caution: These drives do not have onboard internal terminators. The user, systems integrator or host equip- ment manufacturer must provide a terminator arrangement external to the drive when termination is required. For LW drives, terminator modules can be purchased that plug between the SCSI I/O cable and the drive I/O connector or on the end of a short I/O cable stub extending past the last cable connector. LC drives are designed to be plugged into a backpanel connector without cabling.

9.9Terminator power

LW drives

You can configure terminator power from the drive to the SCSI bus or have the host adaptor or other device supply terminator power to the external terminator. See Section 8.1 for illustrations that show how to place jumpers for this configuration.

LC drives

These drives cannot furnish terminator power because no conductors in the 80-pin I/O connector are devoted to terminator power.

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Contents Cheetah 36XL Family ST336705LW/LC ST318405LW/LC ST39205LW/LC Page Cheetah 36XL Family ST336705LW/LC ST318405LW/LC ST39205LW/LC Page Revision Date Writer/Engineer Sheets Affected Revision status summary sheetPage Contents Installation Defect and error managementSeagate Technology support services Interface requirementsCheetah 36XL Product Manual, Rev. E Vii List of FiguresPage Cheetah 36XL family drive ST336705LC shown ScopeCheetah 36XL Product Manual, Rev. E Applicable standards and reference documentation Australian C-Tick Korean MICTaiwanese Bsmi General description Cheetah 36XL family drive Media characteristics Cheetah 36XL Product Manual, Rev. E Standard featuresPerformance ReliabilityOptions factory installed Factory installed accessoriesFormatted capacities Programmable drive capacityPerformance characteristics Ultra2 Scsi Ultra160 Scsi Start/stop timePrefetch/multi-segmented cache control Caching write data Cache operationPrefetch operation Cheetah 36XL Product Manual, Rev. E Cheetah 36XL Product Manual, Rev. E Reliability specifications Preventive maintenance Reliability and serviceService life Service philosophyControlling S.M.A.R.T 7 S.M.A.R.TReporting control Performance impactDetermining rate Predictive failuresDST Failure Definition State of the drive prior to testingImplementation Invoking DSTShort test Function Code 001b Product warrantyExtended test Function Code 010b Log page entriesProduct repair and return information Cheetah 36XL Product Manual, Rev. E Physical/electrical specifications AC power requirementsDC power requirements Power sequencing Conducted noise immunity3 12 V Current profile Typical ST336705 drive +12 V current profile Typical ST39205 drive +12 V current profile TypicalST318405 drive +5 V current profile Power dissipation ST336705 Os per Second Cheetah 36XL Product Manual, Rev. E ST318405Temperature ST39205Environmental limits Effective altitude sea level Relative humidityShock and vibration ShockPackage size Packaged/product weight Drop height Recommended mounting Air cleanliness VibrationAcoustics LW mounting configuration dimensions LC mounting configuration dimensions Defect and error management Drive error recovery proceduresDrive internal defects Scsi systems errors Configure drive options InstallationFormatting Drive ID/option select headerDo not install jumpers retain cover J5 jumper header on LW model only J2 option select header Does not apply to LC models Cheetah 36XL Product Manual, Rev. E Function descriptionCooling Drive orientationDrive mounting GroundingScsi interface messages supported Interface requirementsScsi interface commands supported Cheetah 36XL Product Manual, Rev. E Commands supported by Cheetah 36XL family drive Inquiry Vital Product data Mode Sense dataCheetah 36XL Product Manual, Rev. E Mode Sense Data Cheetah 36XL Product Manual, Rev. E Mode sense data, ST318405 values Bytes Cheetah 36XL Product Manual, Rev. E Mode sense data, ST39205 values Bytes Cheetah 36XL Product Manual, Rev. E Condition/features supported DC cable and connector 2 REQ/ACK offsetPhysical interface Pin Power Scsi interface cable requirements Scsi interface physical descriptionMating connectors for LW model drives Mating connectorsMating connectors for LC model drives ST336705LC, ST318405LC and ST39205LCScsi ID Right-angle to Pcba connectorsNonshielded 68 pin Scsi device connector used on LW drives Nonshielded 80 pin Scsi SCA-2 connector, used on LC drives GND +DBP1 Charge 68Cheetah 36XL Product Manual, Rev. E Multimode signals Electrical descriptionMultimode-SE and LVD alternatives Input characteristics Output characteristicsTerminator requirements Terminator power LW drives General cable characteristicsLow voltage differential I/O circuits LC drivesDisc drive Scsi timing Drive activity remote LED signal status Cheetah 36XL Product Manual, Rev. E Automated Services Seagate Technology support services Online ServicesPresales Support Technical SupportCustomer Service CSO USA/Canada/Latin America Support ServicesEuropean Support Services Africa/Middle East Support Services Asia/Pacific Support ServicesCall Center Toll-free Direct dial Cheetah 36XL Product Manual, Rev. E Index Symbols Cheetah 36XL Product Manual, Rev. E LED PCB System chassis Page
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