16.1. Command Description
The MODE SENSE command provides a means for the Drive to report parameters to the Initiator. It is a complementary command to the MODE SELECT command.
The Drive will implement only one common set of parameters for all Initiators.
The MODE SENSE parameter list will be returned during the DATA IN phase of the command.
If disconnection is allowed, the Drive will only disconnect when execut-ing this command if the previous command was an immediate type com-mand.
When page format is used the MODE SENSE command may return 4 different types of parameters; current values, changeable values, default values or saved values.
The current values are the values under which the Drive is presently configured for the page specified. The current values returned are:
1) The parameters set in the last successful MODE SELECT com-mand.
2) The saved values if a MODE SELECT command has not been executed since the last power-up, RESET condition or BUS DEVICE RESET message.
3) The default values if a MODE SELECT command has never been executed with the save parameter (SP) bit set.
Changeable Values The page requested will be returned containing information that indi-cates which fields are changeable. Parameters that are changeable will be set to one. Parameters that are not changeable will be set to zero. If any part of a field is changeable all bits In that field will be set to one. If none if the parameters are changeable within a page, the Page Length value will be set to zero.
Default Values The default values are set once and for all in the Drive's production line.
Saved Values
Default values are located in the EEPROM. Parameters not supported by the Drive will be set to zero.
The saved values are the values saved by the last successful MODE SELECT command with the save parameter (SP) set or the default val-ues if no MODE SELECT with the SP bit has never been executed.
Saved values are located in the EEPROM. Parameters not supported by the Drive will be set to zero.
16-1 SCSI-2 Functional Specifications
BYTE
Tandberg Data Mode Sense
16.2. Command Descriptor Block
BIT 7 6 5 4 3 2
, o
Table: MODE SENSE Commaiul Block
A Disable Block Descriptor (DBD) bit of one indicates that the Block Descriptor List will not be transferred to the Initiator. A DBD bit of zero indicates that the Block Descriptor List will be transferred following the Header List.
The page control (PC) field defines the type of parameter values to be re-turned.
0: Return current values 1 : Return changeable values 2: Return default values 3: Return saved values
The page code specifies which page(s) to return.
NOTE:
The special page code 3Fh can be used to have the Drive return all its page descriptors.
- Legal values are OOh, Olh, 02h, 10h, Uh, 20h, 21h, 22h and 3Fh.
Page Code OOh is returning the Header List followed by the Block De-scriptor List - a total of 12 bytes. When selecting Page Code OOh the DBD bit is ignored.
See the MODE SELECT command for a description of the various pages.
Allocation Length This field specifies the maximum number of bytes that the Initiator has allocated for the returned MODE SENSE data. An Allocation Length of zero indicates that no MODE SENSE data will be sent. The Drive termi-nates the DATA-IN phase when Allocation Length bytes have been transferred or when all available MODE SENSE data have been trans-ferred, whichever is less.
ltr2 SCSI-2 Functional Specifications
BYTE BIT 7
16.3. Parameter List
J
6.3.J.
Header ListThe MODE SENSE parameter list consists of three sub-lists. The first list is a 4 byte Header List. This may be followed by a 8 byte Block De-scriptor List. At last there may be one or 7 Page DeDe-scriptor Lists. ,.
6 5 4 3 2 1
o
Table: MODE SENSE Header List
This field specifies the length in bytes of the following MODE SENSE data (the Sense Data Length byte itself is not included) that is available to be transferred during the DATA IN phase
This field will indicate the type of cartridge inserted into the Drive.
OOh
The Write Protect (WP) bit of zero indicates that the cartridge is write enabled. A WP bit of one indicates that the cartridge is write protected.
The Drive supports the following mode: 0 and 1. Mode 0 indicates that the WRITE (and COPY (copy function
=
backup) and WRITE FILE-MARKS) command reports GOOD status when the requested data blocks have been actually written and verified. Mode 1 indicates that the WRITE (and COPY, WRITE FILEMARKS) command reports GOOD status as soon as the requested data has been transferred into the Drive's data buffer.1~3 SCSI-2 Functional Specifications
Tape Speed
Block Descriptor Length
Tandberg Data Mode Sense
This field specifies the current tape speed. The following values are legal:
Oh: Default
The actual speed depends on the current tape format:
I
Tape FormatI
Tape Speed OIC-241120/150 96 IpsOIC-525 120 Ips
OIC-1000 53 Ips
2h: 80 ips when the Drive is in QIC-IOOO mode.
This field specifies the length in bytes of the block descriptor list. It will always be set to 8.
76-4 SCSl-2 Functional specifications
(
BYTE
00 01 02 03 04 05 06 07
Density Code
16.3.2. Block Descriptor List
BITT 6 5 4 3 2 1
o
Density Code
I
Number of Blocks
RESERVED Block Size
Table: MODE SENSE Block Descriptor List
This field indicates the current operating tape fonnat. The Density Code value returned in response to a MODE SENSE command will be as described below:
• The tape format will be set Unknown when the Drive has reported Unit Attention due to power-up / reset or when a new cartridge has been inserted. The tape format will remain Unknown until a read / space or write type operation has been performed.
• When a successful read / space type command has been performed the Density Code will be automatically updated to reflect the format on the tape just read.
• When a write type command has been performed the Density Code will be set equal to the density code used by the last write type command. See the corresponding {reld in the MODE SELECT command for details. .
Possible Density Codes are:
OOh Unknown OSh QIC-24 OFh QIC-120
10h QIC-150 11h QIC-S25 1Sh QIC-1000
Number Of Blocks This field will always be set to zero to indicate that the whole tape has the same density code and block length.
Block Size This field reports the currently configured fixed block size. See the corresponding field in the MODE SELECT command for details.
16-5" SCSl-2 Functional SpecificatiOns
Tandberg Data Mode Sense
16.3.3. Error Recovery Page Descriptor
See the MODE SELECT command for details on the current, saved and default values of this page (Page Code Olh)
The PS bit will be set to one for this page.
The Changeable Values page will return the following values:
Byte 00
OSh The OCR and PER bits are changeable FFh Read Retry Count Is changeable OOh
OOh OOh OOh
FFh Write Retry Count Is changeable OOh
OOh OOh
16.3.4. Disconnect/Reconnect Page DeSCriptor
See the MODE SELECT command for details on the current, saved and default values of this page (Page Code 02h)
The PS bit will be set to one for this page.
The Changeable Values page will return the following values:
16-6
FFh Read Buffer Full Ratio Is changeable FFh Write Buffer Empty Ratio Is changeable OOh
16.3.5. Device Conflgurafion Parameters Page Descriptor See the MODE SELECT command fOT details on the current, saved and default values of this page (Page Code lOh)
The PS bit will be set to one for this page.
The Changeable Values page will return the following values:
Byte DO
FFh Active Partition is changeable FFh Write Buffer Full Ratio Is changeable FFh Read Buffer Empty Ratio Is changeable FFh Write Delay Time Is changeable
16.3.6. Medium Partition Parameters Page Descriptor See the MODE SELECT command for details on the current, saved and default values of this page (Page Code llh)
The PS bit will be set to one for this page.
The Changeable Values page will return the following values:
16-7