Quantum Instruments DLT 7000 manual Wide Data Transfer Request Message 01h

Messages

4.2.16 WIDE DATA TRANSFER REQUEST Message (01h)

The following figure illustrates the message formats.

Bit	7	6	5		4	3	2	1	0
Byte
0				Extended Message Identifier (01h)
					(see Figure 4-1)

1

Extended Message Length (02h)

2

WIDE DATA TRANSFER REQUEST

3

Transfer Width Exponent

Figure 4–5 Wide Data Transfer Request Message - Data Format

A WIDE DATA TRANSFER REQUEST Message exchange is initiated by a SCSI device whenever a previously arranged transfer width agreement may have become invalid. The agreement becomes invalid after any condition that may leave the data transfer agreement in an indeterminate state such as

∙After a hard reset condition

∙After a BUS DEVICE RESET Message

∙After a power cycle.

The WIDE DATA TRANSFER REQUEST Message exchange establishes an agreement between two SCSI devices on the width of the data path to be used for DATA phase transfer between them. This agreement applies to DATA IN and DATA OUT phases only. All other information transfer phases must use an 8-bit data path.

The DLT 7000 tape drive implements both wide data transfer option and synchronous data transfer option. It negotiates the wide data transfer agreement prior to negotiating the synchronous data transfer agreement. If a synchronous data transfer agreement is in effect, then after accepting a WIDE DATA TRANSFER REQUEST message, it resets the synchronous agreement to asynchronous mode.

Quantum DLT 7000 Tape System 4-13