114 Product Manual - Disc Drive SCSI-2/SCSI-3 Interface (Vol. 2; Ver. 2), Rev. E
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Table 5.1.3.2-4. Log Parameters
Bit
7
6
5
4
3
2
1
0
Byte(s)
0
(MSB)
Parameter Code [1]
1
(LSB)
2
DU
DS
TSD
ETC
TMC
RES-
LP
[2]
[3]
[4]
[5]
[6]
RVD
[7]
3
Parameter Length (n-3 bytes)
[8]
4
- -
- -
:
- -
Parameter Value [9]
- -
n
Notes for Table 5.1.3.2-4
[1] The parameter code field identifies the specific parameter that is being transferred with the Log Page.
These codes are listed and explained in the individual page code descriptions following Table 5.1.3.2-6.
Byte 2 is referred to as the parameter control byte. The meanings of the various fields are discussed in notes
[2] through [7]. For a Log Select command these bits perform a control function, but on a Log Sense com-
mand they only report the drive settings of these bits in this same format on the data-in part of the Log Sense
command.
[2] Disable Update (DU). For the Log Select command, this applies only to the cumulative log parameter
values (indicated by 01 in the PC field of the Log Select and Log Sense command descriptor block). The
drive can set this bit to one or zero also (see note [7] following).
The DU flag bit is defined as follows:
(a) A zero value indicates that the drive shall update the log parameter value to reflect all events that
should be logged by that parameter.
(b) A one value indicates that the drive shall not update the log parameter value except in response to a
Log Select command that specifies a new value for the parameter.
The DU flag is set to one when the current cumulative value of the parameter counter it controls reaches
its maximum value (see Note 8). Upon reaching this maximum value, the data counter does not wrap
around and start over at zero. Incrementing of other counters within the same log pages ceases. Counters
do not restart automatically if the overflowed counter is re-inialized. If the data counter reaches its maxi-
mum value during the execution of a command, the drive completes the command. Drive counter up-
dates are performed in the background. This means a counter may overflow long after a command has
completed, so the drive must treat this condition as a Unit Attention with the Additional Sense code set to
Log Counter at max for all initiators if RLEC=1 (Report Log exception condition bit of the Control Mode
Page 0Ah).
Since the drive uses volatile memory to hold cumulative values, they will be lost when a power cycle
occurs. Unless the initiator commands the drive to save them to non-volatile memory using a Log Select
or Log Sense command with the SP bit set to one.
