Exabyte EXB-8505 8mm manual Read Operations, 2Data flow during a read operation

3 Functional Description

Read Operations

Figure 3-2 provides a high-level overview of the tape drive’s flow of

data during a read operation.

Uncompressed data

1

Data read from tape

SCSI bus

Decompression

circuit

2	Data
	buffer

Data to be decompressed

Tape

Figure 3-2Data flow during a read operation

The process for reading logical blocks of user data is outlined below.

①The tape drive reads data from tape, uses ECC to correct errors as necessary for each physical block, and transfers data to the data buffer. The read operation continues until the buffer is full and tape motion stops.

②If the data has not been compressed, the data goes directly from the data buffer to the SCSI bus.

If the data has been compressed, the data goes from the data buffer to the decompression circuit to be decompressed. Then, the decompressed data is sent to the SCSI bus.

In either case, the 2-byte logical block CRC, which was appended when the data was written, is again verified. This final integrity check assures that all block reconstruction and decompression was successful.

May 1994	EXB-8205 and EXB-8505	3-7
	(Standard and XL)