Command examples, Single command example | Seagate Ultra 320

7.4Command examples

7.4.1Single command example

A typical operation on the SCSI bus is likely to include a single READ command to a peripheral device such as the drive. This operation is described in detail starting with a request from the initiator. This example assumes that no linked commands and no malfunctions or errors occur and is illustrated in Figure 19.

The initiator has active pointers and a set of stored pointers representing active disconnected SCSI devices (a SCSI initiator port without disconnect capability does not require stored pointers). The initiator sets up the active pointers for the operation requested, arbitrates for the SCSI bus, and selects the drive. Once this pro- cess is completed, the drive assumes control of the operation.

The drive obtains the command from the initiator (in this case a READ command). The drive interprets the command and executes it. For this command, the drive reads the requested data from the Disc Media and sends this data to the initiator. After sending the read data to the initiator, the drive sends a status byte to the initiator. To end the operation, the drive sends a Command Complete message to the initiator and then goes to the Bus Free state.

Start

Bus Free

Arbitrate

Status In

Message In (command complete)

Select (no attention)

Bus Free

Command (ex. read)

End

Data In

Figure 19. Single command example

140	Parallel SCSI Interface Product Manual, Rev. A

Image 154

Seagate Ultra 320, Ultra 160 manual Command examples, Single command example

Contents

Parallel Scsi Interface Page Parallel Scsi Interface Page Revision status summary sheet Revision Date Writer/Engineer Parallel Scsi Interface Product Manual, Rev. a Table of Contents Parallel Scsi Interface Product Manual, Rev. a Logical characteristics Wide transfer Message system specification Scsi commands Miscellaneous Scsi bus characteristicsSPI information units Drive features List of Figures Xii Parallel Scsi Interface Product Manual, Rev. a How to use this interface manual Interface requirements Scope of Scsi standards General interface description Applicable standards Glossary Scsi client-server modelPage Page Page Page Page Page Keywords Summary of Scsi messages Physical interface characteristicsMessage Name Hex Code Number Scsi bus Scsi IDs and associated Scsi bus arbitration priorities Priority Scsi bus signals overview Pcrc signal usage requirements Scsi target usage of Pcrca SE signals Signal statesSignal values LVD signals OR-tied signals Voltage and current definitions Data bit P cable Data bit a cable I/O DB15-8 Scsi bus phase Signal sourcesSignal sources DB7-0 Timing Scsi bus timingScsi bus control timing values in nanoseconds Reference Type Value ns Unless Timing description Nanoseconds unless otherwise noted Scsi bus data and information phase ST timing valuesTiming values for negotiated transfer rate Timing values for negotiated transfer rate in nanosecondsPage ATN transmit setup time Min Receive Scsi bus data and information phase DT timing values Fast-160 Fast-320 Comments Total transmitter error budget Receiver errorsInterconnect and system margin Crosstalk time shift ATN transmit setup timeATN receive setup time ISI of data Bus set delay Bus clear delayBus free delay Bus settle delay PCRC receive setup time Flow control receive setup timeFlow control transmit setup time PCRC transmit setup time Power on to selection Data release delayPhysical disconnection delay QAS arbitration delay Receive internal hold time Receive internal setup timeReceive setup time Receive negation period Reset to selection Reset delayReset hold time Residual skew error Strobe offset tolerance System deskew delaySkew correction range System noise at launch Measurement points Clocking methods for data transfers LVD measurement points ST latching data vs. DT latching data Paced transfer on a Scsi bus DT synchronous transfer example Synchronous transfers Data transfer modesAsynchronous transfers Paced transfers Data group transfers ST Data phase parallel transfersDT Data phase parallel transfers Information unit transfers Negotiation Negotiation algorithm Negotiable fields and effects of successful negotiation When to negotiateNegotiable fields Negotiation message pair Field name Response shall be Responding message requirementsField Name Message Numerically Transfer agreements Value Description Message Transfer rate Transfer period factorTransfer period factor relationships Synchronous 12.6 REQ/ACK offset Transfer width exponent Protocol options bits Protocol optionsIureq PPR negotiation setting Iureq to zero Bus phases resulting from Iureq changesSdtr negotiation PPR negotiation setting Iureq to one PPR negotiation keeping Iureq set to zero RTI Retain Training Information WrflowRdstrm Pcompen Transfer Negotiable field combinationsTransfer Period Message restrictions Negotiation message sequences Parallel Scsi Interface Product Manual, Rev. a BUS Free phase Scsi bus phases overviewUnexpected and expected bus free phases Expected bus free phases Arbitration and QAS overview Normal Arbitration phase QAS phase overview QAS protocol Selection phase Information unit transfers enabled Information unit transfers disabledSelection overview Selection using attention condition timeout procedure Reselection phase overview Reselection phasePhysical reconnection Physical reconnection timeout procedure Scsi bus fairness Information transfer phases Information transfer phasesSignal Phase Direction of transfer Comment Synchronous transfer Asynchronous transferST synchronous data transfer DT synchronous transfer Information unit transferPage Data group data field transfer Page Page Page Paced transfer Paced transfer training pattern Start of section a DT Data in phase training patternStart of section B DT Data OUT phase training pattern Start of section C 3.2 P1 data valid/invalid state transitions Starting pacing transfers at end of training pattern Starting pacing transfers with no training pattern Ending pacing transfers Paced information unit transfer Deskewing Wide transfer Command phase Data phase Status phase Message phase Message OUT phase Signal restrictions between phasesMessage in phase exception condition handling Message OUT phase exception condition handling Scsi bus phase sequences Scsi bus phase sequences overview Hard reset or protocol error Reselection Selection Arbitration DT Data Message OUT Data bus protection ST data bus protection using parityParity checking rules for Selection and Reselection phases Data bus protection overview Error detection capabilities Order of bytes in the CRC field General message protocols and formats Message formats Two-byte messages Message formatOne-byte messages Extended messages Extended Message Codes Message categoriesLink Control Messages Link Control message codes Key Identify message format DisconnectIdentify Bit Byte Ignore field definition Ignore Wide ResidueIgnore Wide Residue message format Invalid data bits Message Parity Error Initiator Detected ErrorLinked Command Complete Message Reject Modify Data Pointer message format Modify Bidirectional Data Pointer Modify Bidirectional Data Pointer message format No Operation Parallel Protocol Request Parallel Protocol Request message format Value 00h 01h-FEh FFh Description Timing values Valid protocol options bit combinations Use ST Data in and ST Data OUT phases to transfer dataUse QAS for arbitration Parallel Protocol Request messages implied agreement QAS Request Restore PointersSave Data Pointers Synchronous Data Transfer Request Synchronous Data Transfer Request message format Sdtr messages implied agreements Initiator initiated Sdtr negotiation Target initiated Sdtr negotiationTask Complete Wide Data Transfer Request Wide Data Transfer Request message format Target initiated Wdtr negotiation Wdtr message implied agreementResponding Scsi device Wdtr response Implied agreement Task attribute messages Task attribute message overview and codes ACA Auto Contingent Allegiance Task attribute message codesACA message format Head of Queue Ordered Abort Task Task management messagesTask management message codes Task management message codes 0Eh Abort Task SET Logical Unit ResetTarget Reset Clear ACA Miscellaneous Scsi bus characteristics Bus reset condition Hard reset Reset events Asynchronous condition recovery Active pointers Saved pointers Asynchronous event notification Command processing considerations and exception conditionsIncorrect initiator connection Unexpected Reselection phase SPI information units Information unit transfer logical operationsPage Parallel Scsi Interface Product Manual, Rev. a 115 116 Parallel Scsi Interface Product Manual, Rev. a Parallel Scsi Interface Product Manual, Rev. a 117 SPI command information unit SPI information units SPI command information unit Bit Byte Task Attribute Codes Description Task Management flags Codes Description SPI LQ information unit SPI LQ information unit Bit Byte Bidi Direction F0H SPI LQ information unit typeCodes Type Description FFh AllPage SPI data stream information unit SPI data information unitSPI data information unit Bit Byte SPI status data stream information unit Bit Byte SPI status information unit Bit Byte SPI status information unitReserved Reserved for FCP Packetized Failures code Codes Description SPI command information unit fields invalidPacketized Failures field Bit Byte Task management function not supportedPage 130 Parallel Scsi Interface Product Manual, Rev. a Command Descriptor Block CDB Command implementation requirementsReserved Page Fixed and variable length Command Descriptor Block formats Typical CDB for 16-byte commands Bit Byte Typical CDB for 12-byte commands Bit ByteAdditional CDB Data if required Typical variable length CDB Bit Byte Operation Code 7Fh Additional CDB Length n-7Page Naca a Control field Bit Byte LastLink b Status Status precedence Command examples Single command example Disconnect example Disconnect example Timing examples Auto Contingent Allegiance or Contingent Allegiance Overlapped commands Clearing an Auto Contingent Allegiance condition Sense data Incorrect logical unit selectionAsynchronous Event Reporting Autosense Unit Attention condition Queued tasks formerly queued I/O processes Target hard resetLogical unit reset Untagged task queuing Tagged task queuing Parameter rounding Programmable operating definition Incorrect initiator connection Self-test operations Default self-testS.M.A.R.T. system Short and extended self-tests Background mode Foreground modeSelf-test modes Exception commands for background self-tests Device type a Command Reference All device types Error detection for asynchronous information phases Self-test mode summaryProtection code Covered signals Word Location Signal MeaningPage Code description Error detection propertiesProtection code usage Enabling protection code checking Error handlingProtection code transmission Disabling protection code checking Case 1-Power off during removal or insertion SPI-3 to SCSI-2 terminology mapping SPI-3 to SCSI-2 terminology mappingSPI-3 equivalent term SCSI-2 term Index Code value reserved Disconnect privilege 148 domain 5, 9 dormant Initiator 3, 6, 14, 131, 140 faulted Multidrop 7 multimode Page Scsi Page Wdtr 40 170 Parallel Scsi Interface Product Manual, Rev. a Page Seagate Technology LLC