CDC Wren Mode Page

[neese at adaptex.UUCP]

Okay, its been requested enough.  Here is the mode page for the CDC
Wren IV and > drives, that is used for disabling/enabling the read
ahead buffer.

Mode Sense Command:
Bits	7	6	5	4	3	2	1	0

Byte
0	0	0	0	1	1	0	0	1	1Ah
1	<      LUN      >      	0	0	0	0	0
2	<  PCF	>	<		PAGE CODE		>
3	0	0	0	0	0	0	0	0
4	<		ALLOCATION LENGTH			>
5	0	0	0	0	0	0	0	0

LUN =			Logical Unit Number.  Almost always zero.

PAGE CODE =		For this page is 38H

ALLOCATION LENGTH = 	For this page is 28 bytes.


Mode Select Command:
Bits	7	6	5	4	3	2	1	0

Byte
0	0	0	0	1	0	1	0	1	15h
1	<      LUN      >      <PF>	0	0	0     <SMP>
2	0	0	0	0	0	0	0	0
3	0	0	0	0	0	0	0	0
4	<		PARAMTER LIST LENGTH			>
5	0	0	0	0	0	0	0	0

LUN = 	Logical Unit Number of the SCSI drive.  Usually zero, not to be
	confused with the target ID.

PF =	Page Format bit.  Always set to one.

SMP =	When set to one, causes the drive to save the page permanently else
	the page is saved until the next SCSI reset or power down.

The PARAMETER LIST is made up of 4 byte header and 8 bytes of media
information.  These bytes are gotten via a mode sense command.  The bytes
followng this information is the actual mode page bytes.

Mode Select Page 38H
Bits	7	6	5	4	3	2	1	0

Byte
0      <PS>	0	1	1	1	0	0	0	38H
			PAGE LENGTH
1	0	0	0	0	1	1	1	0	14
2     	0	0	0     <CE>	0	0	0	1
3	1	1	1	1	1	1	1	1
4	0	0	1	1	0	1	0	0
5	0	0	0	0	0	0	0	0
6	0	0	0	0	0	0	0	0
7	0	0	0	0	0	0	0	0
8-15	<		RESERVED (Must be set to zero)		>

Byte 14 (starting at zero) is the byte that contains the CE bit.

CE =	When set (1), the drive will perform read look aheads.  When set
	to zero (default) the drive will not perform read look aheads.


			Roy Neese
			Adaptec Central Field Applications Engineer
			UUCP @ {merch,texbell,killer}!cpe!adaptex!neese