Seagate Technology 10002475-003, Product Description Manual

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Tape Format Chapter 6
Product Description Manual Page 57
Figure 6-1
General Track Layout
Frame
N+1
Frame Frame Frame Frame
N N+2 N+3 N+4
Frames are numbered indirectly using the 26 most significant bits of the
Physical Block Address. Frame operation is controlled by the drive and
generally invisible to the host. Frames are used primarily as a means to control
the error correction operations.
Frames can be overwritten with new data frames or an end-of-data (EOD)
frame. Append operations can only begin at EOD.
An underrun is not allowed in the middle of a frame, regardless of the frame
type. Filler blocks can be used to complete a frame as long as they are not used
interior to a logical block.
A frame that cannot be completed on one track is rewritten in its entirety at the
beginning of the following track. Frames are not split around corner turns.
The general frame layout—52 data blocks and 12 ECC blocks—is illustrated in
Figure 6-2.
Figure 6-2
General Frame Layout
Data
Block Data Data Data
Block Block Block
0 1 2
. . . . .
51
ECC ECC
Block Block . . . . .
0 11
The four types of frames are as follows:
z Data frames contain data and information blocks in addition to ECC
blocks.
z The Media Header frame contains only Media Header blocks and ECC
blocks. This frame is recorded as the first frame on the Directory Track.
z Track ID frames are recorded as part of the preformatting process of the
cartridge. These frames are easily distinguished from other frame types
because they reside entirely outside of the data region of the tape.
z An EOD frame is an absolute indicator of the end of the recorded data. It is
recorded after the last frame containing host data upon terminating a
Write process.