Intel SPSH4 - Server Platform - 0 MB RAM, Technical Product Specification

Page: 73 / 118

SPSH4 Server SystemTechnical Product Specification
Revision 1.11
Intel reference number 10736
61
6.5.1.2 SCSI Memory Region (9000h – 9FFFh)
Buffer memory area for DMA transfers on the SCSI interface. Accesses to this region activate
the appropriate DACK_L and Read/Write strobes to the 53C80S SCSI chip (which has been
properly configured for DMA operations).
6.5.1.3 Drive Power Control/Status Region (A000h – AFFFh)
A read operation of any byte address within this region produces the current value of the Power
Control byte. This value does not report the actual state of drive power (e.g., whether or not
drive power is within specifications). Instead, this indicates whether the power for a particular
drive has been switched on or off.
A write operation to any byte address within this region updates the current value of the Power
Control byte, which causes selected drive slots to power on or off. The initial (default) value is
11011111b (all drives on). This allows normal server operation even if the firmware is corrupted
or the microcontroller is not operational. The lower five bits function as power switches for each
drive slot. The remaining three bits are read-only, and are defined below.
!WARNING!
If a drive is powered up immediately upon detection, it is likely to be
damaged, as the drive will not be fully seated. It is recommended that
firmware “debounce” the drive presence detect bits, and power up the
drive no less than 250ms after the drive is detected as being present.
Table 48: Drive Power Status Byte Format
Bit(s) Name Description
7 Internal/External Read only. Logic 1 indicates the backplane is installed in an “internal” chassis. Logic 0
indicates the backplane is installed in an “external” chassis (e.g. peripheral box).
6 Reserved Reserved for future use.
5 SCSI ID Read only. This bit determines the SCSI ID for the drive array.
4::0 DRVPWR[4::0] Drive power control bits (read/write). Bit 0 corresponds to drive 0, bit 1 to drive 1, and so
on. An active bit (1=active) indicates power is turned on for that drive; an inactive bit
indicates power is turned off for that drive. Writing a 1 to a bit position turns on, or
maintains power on, for the associated drive.
6.5.1.4 Fault Indicator Control Region (B000h – BFFFh)
A write operation to any byte address controls drive fault indicator LEDs. The value is initially
00h, which means all drive-fault LEDs are off. The lower five bits of the data byte function as
on/off switches for each LED.