Quantum 1200 Series DAT Autochanger Betriebsanweisung PDF herunterladen (Seite 41)

SDLT 600 SCSI Interface Guide Chapter 3: SCSI Messages

81-81200-02 REV A01 January 2005 3-13

This agreement applies to the DATA IN and DATA OUT phases only. All other information transfer

phases must use asynchronous transfers.

The SDLT tape drive implements both the wide data transfer and synchronous data transfer options. If

both wide and synchronous data transfers are used, the wide data transfer agreement must be

negotiated first. If a synchronous data transfer agreement is in effect, the drive resets the synchronous

agreement to asynchronous mode after accepting a WIDE DATA TRANSFER REQUEST message.

If the Transfer Period requested is less than the minimum value the drive supports, the drive adjusts the

return value up to the minimum supported value.

Not all possible transfer periods between the minimum and maximum values are supported. If the

Transfer Period requested is between the minimum and maximum supported values, but not exactly

achievable by the drive, the drive returns the request value and the drive transmits data at the next

lower speed it is capable of. The initiator may send data at the request speed. The maximum supported

synchronous period is 5Dh (372 nsec). A request with a Transfer Period less than this returns a request

for asynchronous mode.

The drive’s minimum supported value for Transfer Period is 0Ah when the bus is operating in LVD

mode. When operating in SE (Single-Ended) mode, the minimum Transfer Period value is 0Ch.

When the Transfer REQ/ACK value is non-zero, the drive will transfer data using synchronous

transfers; a Transfer REQ/ACK offset value of zero indicates asynchronous transfers. If the host

requests a Transfer REQ/ACK offset value greater than the maximum value that the drive supports, the

drive responds with the maximum value that it supports.

Table 3-9. Transfer Periods and Transfer Rates

Transfer Period Transfer Rate

0Ah 40 MHz, 25 nsec Transfer Period

0Bh 33 MHz, 30.3 nsec Transfer Period; Super DLTtape uses 37.5 nsec period

0Ch 20 MHz, 50 nsec Transfer Period

0Dh – 5Dh (4 * Transfer Period) nsec

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Quantum 1200 Series DAT Autochanger Betriebsanweisung Seite 41