Quantum Audio Travan 40 Tape Drive STT3401A - Manual (Page 77)

ATAPI Interface Chapter 5
Seagate Travan 40 Product Manual Page 69
READ BUFFER (Group 1, Op. Code 3C)
The READ BUFFER command will cause the contents of the drive’s data buffer to be
returned to the Host and is intended to be used in conjunction with the WRITE
BUFFER command as a Diagnostic tool. Using Buffer I.D. and Buffer Offset, the
data transfer may be started from any location in the buffer. This command tests the
ATAPI Bus and the drive’s Data Buffer. The tape is not affected.
CDB for READ BUFFER Command
Data Bits
Byte 7 6 5 4 3 2 1 0 Hex
0 0 0 1 1 1 1 0 0 3C
1 0 0 0 0 0 Mode 0X
2 Buffer I.D. XX
3
4
5 MSB
Buffer Offset
LSB
XX
XX
XX
6
7
8 MSB
Transfer Length
LSB
XX
XX
XX
9 0 0 0 0 0 0 0 0 00
MODE: The Mode field determines the format of the data that is returned to the
Host.
Mode Type Description
0-1h Reserved
2h Data Only Mode The drive will send the data only, and no header.
3-7h Reserved
Buffer I.D.: The data buffer is divided into 256 equal segments of 2048 bytes each.
The number of each segment is specified by the Buffer I.D. To perform a read buffer
at the first segment (or beginning) of the buffer, a Buffer I.D. of 00h must be
specified. To perform a read buffer at the 128
th
segment, a Buffer I.D. of 7Fh must
be specified (etc.).
Buffer Offset: This field specifies the byte location in the specified buffer in which
the first data byte to be transferred to the Host will be found. Offset values greater
than 7FFh will cause Check Condition, Illegal Request.
Transfer Length: This field specifies the number of bytes to be read from the Buffer
by the Host. The value includes the four-byte Header.
NOTE: The STT3401A has an 8 MB buffer. Each segment, as defined by Buffer
I.D., will be 2K bytes in size and the maximum offset will be 7ffh.