User's Guide

Chapter 2 Media Changer Commands
Read Buffer Command (3Ch)
Quantum SuperLoader 3 Software Interface Guide 97
BUFFER
header is followed by data bytes from the target data buffer. The
figure below illustrates the format of the header. The buffer ID must be
set to 0. The buffer offset must be less than the size of the buffer.
Figure 55 Read Buffer Header
Table 45 Read Buffer Header
Data Mode (0010b) 2
In this mode, the DATA IN phase contains only buffer data.The buffer ID
must be set to 0. The buffer offset must be less than the size of the buffer.
Descriptor Mode (0011b)2
In this mode, a maximum of four bytes of READ BUFFER descriptor
information is returned. The device returns the descriptor information for
the buffer specified by the
Buffer ID. In this mode, the device does not
reject the invalid
Buffer IDs with a CHECK CONDITION status, but returns
all zeros in the
READ BUFFER descriptor.
Bit
Byte76543210
0
Reserved
1 - 3
(MSB)
Available Length
(LSB)
Field Description
Available
Length
This field specifies the total number of data bytes available in the target’s
buffer. This number is not reduced to reflect the allocation length, nor is it
reduced to reflect the actual number bytes written using the
WRITE BUFFER
command. Following the
READ BUFFER header, the target transfers data
from its data buffer.