Density Code

7 6 5 4 3 2 1 0 00 Density Code 01 (MSB) Number of Blocks 02 03 (LSB) 04 Reserved 05 (MSB) Block Length 06 07 (LSB)

Byte 00 - Density Code

In the MODE SELECT command, the Density Code field specifies the format in which you want the CTS to write data to tape. In the MODE SENSE command, the Density Code field identifies the current operating density of the CTS.

Table 10-8 lists the valid values for the Density Code.

Note: Refer to Section 10.18 on page 10-61 for examples of using the CTS to write, read, and append data in the various tape formats it supports. Refer to page 10-68 in that section if you want to change the Density Code and you cannot issue MODE SELECT commands.

Restrictions for Setting the Density Code:

The entire tape must be written in the same format. That is, the Density Code applies to the entire tape, not to individual blocks and files. You can change the Density Code only when the tape is logically positioned at LBOT.

For read operations, the CTS automatically determines the correct format.

A blank tape written before the first MODE SELECT command will be written in the power-on default format.

Specify this Density Code... To write data in this format Notes 00h Default format (error checking suppressed)

Use this Density Code at LBOT if you want to write default format tapes (8500c for the EXB-8505; 8200c for the EXB-8205)*. The CTS ignores this Density Code (does not return Check Condition status) if you attempt to use it to change the tape format from a non-default format to the default format when the tape is not at LBOT.

14h

8200 (full error checking)

Use this Density Code at LBOT if you want to write 8200 format tapes.

The CTS returns Check Condition status with the sense key set to Illegal Request (5h) if you attempt to use this Density Code to change the tape format from non-8200 to 8200 when the tape is not at LBOT. 15h (EXB-8505 only) 8500 (full error checking)

Use this Density Code at LBOT if you want to write 8500 format tapes.

The EXB-8505 returns Check Condition status with the sense key set to Illegal Request (5h) if you attempt to use this Density Code to change the tape format from non-8500 to 8500 when the tape is not at LBOT. 7Fh No change in the format (error checking suppressed)

Use this Density Code if you do not want to change the tape format.

The format will remain the same as it was before the MODE SELECT command was sent to the CTS.

8Ch (EXB-8505 only) 8500c (full error checking)

Use this Density Code at LBOT if you want to write 8500c format tapes.

The EXB-8505 returns Check Condition status with the sense key set to Illegal Request (5h) if you attempt to use this Density Code to change the tape format from non-8500c to 8500c format when the tape is not at LBOT.

90h

8200c (full error checking)

Use this Density Code at LBOT if you want to write 8200c format tapes.

The CTS returns Check Condition status with the sense key set to Illegal Request (5h) if you attempt to use this Density Code to change the tape format from non-8200c to 8200c when the tape is not at LBOT.

* An EEPROM option allows you to choose the default format for the CTS (see the “Default write format” option Table 10-8 Values for the Density Code field

As described in Table 10-9, the value reported for the Density Code field by the MODE SENSE command depends on the most recent activity.

If the most recent activity was a...

...then the value reported for the Density Code is the... ... actual format of the data on

the tape (format for reading tape)

...power-on default or format set with the most recent MODE SELECT (format for writing tape)* Power on

(tape not loaded) ✔

Load operation—

previously written tape ✔

Load operation—

blank tape ✔

MODE SELECT ✔

READ ✔

WRITE ✔

* The Density Code reported in these cases reflects the format set by the most recent MODE SELECT command that set the Density Code to a non-7Fh value.

Notes:

The RTF field on the Vendor Unique Parameters Page 1 (Page Code 20h) indicates the format of the data on the currently loaded data cartridge. The WTF field on the same page indicates the format that will be used when the CTS writes data. The values returned for these fields do not depend on the last operation performed by the CTS.

If the tape is written in an unrecognized format or if the CTS is not ready, the Density Code returned by the CTS corresponds to the density in which it would write if the tape were positioned at LBOT (that is, the currently selected write density).

When the CTS appends new data to existing data, it writes the new data in the same format as the data already on the tape. In this case, the writing format is automatically changed to the reading format (no user intervention is required). Once this automatic density change has occurred, it remains in effect for all operations on the particular tape—including the rewriting of LBOT.