HP Q153090901 - Manual (Page 121)

READ BUFFER 3Ch
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READ BUFFER 3Ch
R EAD BUFFER reads data from the memory on the drive and sends it to the initiator. The value of
the Mode field determines whether only the 4-byte descriptor is returned, only the data is returned,
or whether both are returned.
Pre-execution checks:
If any of the following rules are broken then CHECK CONDITION status is reported. Sense data will
be as described in Illegal Field Checks.
Command descriptor block:
CDB fields:
Illegal Field Reservation Deferred Error Unit Attention
7 6 5 4 3 2 1 0
0 Operation Code (3Ch)
1 Reserved(0) Mode
2 Buffer ID
3 (MSB)
Buffer Offset
5 (LSB)
6 (MSB)
Allocation Length
8 (LSB)
9 Control
Mode 00000b A 4-byte descriptor is returned, followed by (Allocation Length − 4) bytes of data.The data
is read from the buffer identified by the Buffer ID, starting from offset zero in the buffer.
The Buffer ID and Buffer Offset must both be 00h.
00010b The drive returns Allocation Length bytes of data which is read from the buffer identified
by the Buffer ID, starting from Buffer Offset bytes from the start of the buffer.
There are no restrictions on the value of Buffer ID and Buffer Offset, except that the Buffer
Offset must be kept within the buffer size.
00011b The drive returns a 4-byte descriptor for the buffer identified by the Buffer ID field. Invalid
buffer IDs will return a buffer descriptor of all zeros.
The Buffer Offset field must be zero.
01010b The drive returns data from the Echo Buffer. The Buffer ID and Offset are ignored.
01011b The drive returns the Echo Buffer descriptor. The Buffer ID and Offset are ignored.
Buffer ID The Buffer ID indicates which buffer is to be read. The buffers are defined as follows:
Buffer ID Memory Area Category Offset Boundary
00h Main buffer memory RAM 4 bytes
01h Processor addressable memory RAM 1 byte