Quantum Instruments DLT 7000 - Manual (Page 94)

Messages
4-4 Quantum DLT 7000 Tape System
Bit
Byte
7 6 5 4 3 2 1 0
0 Extended Message (01h)
1 Extended Message Length
2 Extended Message Code
3 to n-1 Extended Message Arguments
Figure 4–1 Extended Message - Data Format
Table 4–3 Extended Message - Field Description
Field Description
Extended Message Length This field specifies the length, in bytes, of the Extended Message
Code plus the Extended Message Arguments that follow. Therefore,
the total length of the message is equal to the Extended Message
Length plus 2.
A value of 0 for the Extended Message Length indicates that 256
bytes follow.
Extended Message Code The drive supports three Extended Messages. They are: 00h
MODIFY DATA POINTER 01h
SYNCHRONOUS DATA TRANSFER REQUEST 03h
WIDE DATA TRANSFER REQUEST