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16 Chapter 5 : Connecting Hard Disk Drives16 Chapter 5 : Connecting Hard Disk Drives16 Chapter 5 : Connecting Hard Disk Drives
SCSI ID setting
The SCSI bus is a parallel type connection, and data on the bus is available to all devices.
However, communication will usually be between two devices only, so each device is
allocated an ID number, like an address number. In this way, only the device with the ID
number that is specified in the data will actually read and respond to the data.
If two devices share the same ID number, the system will probably crash, so make sure that
each device has its own ID number. SCSI devices usually have a DIP switch or, like the
CBX-D5, a thumb wheel switch for ID setting. Refer to the instructions supplied with your
particular SCSI device.
The Apple Macintosh example above shows six devices connected in a SCSI daisy chain
(seven including the computer). Each device has its own ID number. Note that the last
device in the chain is terminated. On a Apple Macintosh computer, SCSI ID 7 is reserved
for use by the computer, and ID 0 for the internal hard disk. Do not use either of these
IDs for any other SCSI device.
In the Atari ST/STE system shown above, five SCSI devices are connected in a daisy
chain. Hard disks must be set with continuous SCSI IDs starting from 0 (0, 1, 2, 3…).
However, the CBX-D5 can be set to SCSI ID 5 or 6. Do not set any device to SCSI ID 7.
In the Atari TT system shown above, six SCSI devices are connected in a daisy chain. Hard
disks must be set with continuous SCSI IDs starting from 1 (1, 2, 3, 4…). However, the
CBX-D5 can be set to SCSI ID 5 or 6. Do not set any device to SCSI ID 7.
HARD
DISK 1
CBX-D5HARD
DISK 2
SCSI SCSISCSI
ID No. 1 ID No. 2 ID No. 3
HARD
DISK 3
SCSI
SCSI
DEVICE
SCSI
ID No. 4ID No. 5
SCSI
DEVICE
SCSI
ID No. 6
This device is
terminated
SCSI
Adaptor
HARD
DISK 2
HARD
DISK 1
SCSI SCSI
ID No. 0 ID No. 1
ID No. 2
HARD
DISK 3
SCSI
HARD
DISK 4
SCSI
ID No. 3ID No. 6
CBX-D5
SCSI
This device is
terminated
ATARI
ST/STE
19-pin
DSUB
HARD
DISK 1
HARD
DISK 2
HARD
DISK 1
SCSI SCSI
(internal hard disk
set to SCSI ID 0)
ID No. 1 ID No. 2
HARD
DISK 3
SCSI
HARD
DISK 4
SCSI
ID No. 3
ID No. 6
CBX-D5
SCSI
This device is
terminated
ATARI
TT
SCSI
ID No. 4ID No. 5