Quantum 1200 Series DAT Autochanger Podręcznik Użytkownika Pobierz pdf (Strona 38)

Supported SCSI Messages SDLT 600 SCSI Interface Guide

3-10 January 2005 81-81200-02 REV A01

3.2.12 PARALLEL PROTOCOL REQUEST (extended message

04h)

PARALLEL PROTOCOL REQUEST (PPR) messages (as shown in Table 3-4) are used to negotiate

synchronous transfer agreements and wide data transfer agreements, and to set the protocol options

between two SCSI devices.

Figure 3-4. PARALLEL PROTOCOL REQUEST Message — Data Format

The PPR message is required to configure an SDLT tape drive. This command sets the transfer period,

offset, transfer width, and clocking all in one message.

Support for the PPR message is indicated by the Clocking field in the Standard Inquiry page. The PPR

message can also be used to set the transfer period, offset, and transfer width on an SDLT tape drive

with an Ultra 2 interface card. To enable it, set the MODE SELECT Vendor Specific EEPROM

parameter EnablePPRMsg to 1.

The PPR message allows the host and target devices to negotiate operating conditions of the SCSI bus.

An SDLT tape drive responds to a PPR message with a reciprocal PPR message containing acceptable

parameters for the interface. An SDLT tape drive never initiates a PPR negotiation.

Details about how to configure the PPR message are shown in Table 3-8.

Bit

Byte

7 6 5 4 3 2 1 0

Extended Message Identifier (01h)

(see

Figure 3-1)

1 Extended Message Length (06h)

2 Parallel Protocol Request (04h)

3 Transfer Period Factor

4 Reserved

5 REQ/ACK Offset

6 Transfer Width Exponent

Reserved DT_

REQ

Rsv’d

1 2 ... 33 34 35 36 37 38 39 40 41 42 43 ... 293 294

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Quantum 1200 Series DAT Autochanger Podręcznik Użytkownika Strona 38