Reference Guide

Chapter 4 SCSI Commands
READ BUFFER Command (3Ch)
DLT-S4 Interface Reference Guide 267
Combined Header and
Data Mode (00h)
4
In this mode, the drive returns a 4-byte header followed by data bytes.
The drive terminates the DATA IN phase or FCP_DATA IU when the
Allocation Length bytes of header and data have been transferred or
when all available data has been transferred to the initiator, whichever is
less.
The 4-byte
READ BUFFER header is followed by data bytes from the
target data buffer. Figure 130
illustrates the format of the header.
Figure 130 READ BUFFER
Header — Data Format
Table 149 READ BUFFER
Header — Field Description
Data Mode (02h) 4 In this mode, the DATA IN phase or FCP_DATA IU sent to the initiator
contains only buffer data. This mode can be used to check the diagnostic
read buffer to see if an unexpected error has occurred.
Bit
7 6 5 4 3 2 1 0
Byte
0 Reserved
1 — 3
(MSB)
Available Length
(LSB)
Field Description
Available Length Specifies the total number of data bytes available in
the target’s buffer. This number is neither reduced
to reflect the allocation length nor to reflect the
actual number bytes written using the
WRITE
BUFFER
command. Following the READ BUFFER
header, the drive transfers data from its data
buffer.