Fujitsu M2488 manual Page Descriptor Field Description, Mode Settings, Initiator Setup

TAPE UNIT SCSI COMMANDS M2488 PRODUCT GUIDE

Table 4-59. Page Descriptor Field Description

BYTE	BIT	VALUE		DESCRIPTION
0	0-5			Following the block descriptor (if supplied) are MODE SELECT pages. The
				Page Code field identifies the format and parameters for that page. This control-
				ler supports pages 01h (Error Recovery and Reporting), 02h (Disconnect/
				Reconnect control), 0Ah (Control Mode Page), 10h (Device Configuration
				Parameters) and 00h (Vendor Unique Parameters).
0	7		1	When using the MODE SENSE command, a PS bit of one indicates that the
				mode page can be saved by the target in a non-volatile location.
			0	A PS bit of zero indicates that the supported parameters cannot be saved.
1	0-7			The Additional Page Length indicates the number of bytes in that page. The
				additional page length value of each defined page, does not include the Page
				Length byte. The target may return in the pages of the MODE SENSE com-
				mands as many consecutive bytes as it supports, for each page it supports, with-
				out splitting fields of multiple bytes. The page length in the pages of the MODE
				SELECT command must be set to the value returned by the target in the MODE
				SENSE Page Length bytes. Otherwise, the target creates CHECK CONDITION
				status with the sense key of ILLEGAL REQUEST.

4-3.13.3 Mode Settings

When the product is manufactured, the saved mode settings are initialized to the default mode set- tings; the saved mode settings will then change after each successful MODE SELECT with the SP bit equal to 1. Following a power on, SCSI bus reset, or BUS DEVICE RESET message, the saved mode settings are copied into the current mode settings. So, if a MODE SENSE is issued when the box is first shipped (previous to any successful MODE SELECT with SP=1), then the default set- tings will be reported when the PC field selects default, saved or current parameters. Following a power up (after a successful MODE SELECT with SP=1), the saved settings are reported if cur- rent or saved values are selected by the PC field; the default settings are reported if default values are selected by the PC field.

More information on the MODE SENSE command can be found in section 5-2 on page 5-1.

4-3.13.4 Initiator Setup

To ensure that the MODE SELECT command performs the desired operations, it is strongly rec- ommended that the initiator adhere to the following steps:

a.Issue a MODE SENSE command requesting the target to return all Changeable Values (PC field 01b and Page Code 3Fh in byte two of the MODE SENSE CDB) and preserve the “changeable” values,

b.Issue a MODE SENSE command requesting the target to return all Current Values (PC field 00b and Page Code 3Fh in byte two of the MODE SENSE CDB) and preserve the “current” val- ues,

c.Perform a bitwise AND operation of the “current” values with the one’s complement of the “changeable” values, (this step is important because the target will not accept the command if any non-changeable field is set to a value other than the “current” value)

d.Make further desired changes to bytes which are changeable,

e.Make sure that the PS bit in every mode page is 0 (the MODE SENSE command will report a 1 in the PS bit, but a MODE SELECT command will fail if mode pages are sent with the PS bit

4-60 CG00000-011503 REV. A April 1997