SCSI (Small Computer System Interface) allows you to connect external devices such as disk drives, scanners, printers, and some PowerLabs to your computer. SCSI provides reliable, fast data transfer but there are a few peculiarities that are useful to know about. These include SCSI termination, ID conflicts, cards, drivers and cables.
SCSI Compatible PowerLabs and MacLabs
PowerLabs have either SCSI, USB, high speed USB, serial connectors
or a combination of these. The latest PowerLabs have USB only.
The following table lists PowerLab models and their respective
interface(s).
SCSI-Compatible Windows Computers
The majority of Windows computers come with built-in USB
rather than SCSI. However, most Windows computers support
SCSI cards via an ISA, PCI, or PCMCIA bus, and Windows 95,
98, ME, 2000 and XP come with built-in SCSI drivers which
support a wide range of SCSI cards. If you are unsure whether
your computer supports SCSI, ask your local computer dealer.
For further information on using USB see the USB
support page.
SCSI-Compatible Macintosh Computers
With the introduction of the iMac and Blue & White G3,
Apple have made USB their standard interface. Apple no longer
ship Macintosh computers with built-in SCSI. However, older
machines will have SCSI built-in and any PowerPC that has
a PCI or PCMCIA slot will take a SCSI card. The only PowerPCs
that do not support SCSI cards are the iMacs and the iBook.
These have built-in USB and can be used with ADInstruments
USB PowerLabs. See the USB support page for
more information. We do not recommend using a USB to SCSI
adapter with PowerLab. For more information, see the USB
- SCSI adapter support page.
SCSI ID Conflict
It is possible to have a number of devices connected together via SCSI to your computer. This is called a SCSI daisy chain. Each device on this chain needs to have a unique ID number allocated to it before your computer is turned on. To complicate matters, your computer may also reserve some SCSI ID numbers. The computer itself uses ID 7. If you have an internal SCSI device, such as a hard disk or CD-ROM drive, then this will also be allocated a SCSI ID number. If the ID number of any device is the same as any other, including those used by the computer, then you will get a "SCSI ID conflict" and your SCSI device, including your PowerLab, will not be recognized. Even if the PowerLab is the only SCSI device connected to your computer, then you need to ensure it has a unique ID. PowerLabs are shipped with their SCSI ID number set to 4 as this ID is typically not used by other devices. The SCSI ID should not be reset unless the PowerLab is turned off. There are buttons on the back of your PowerLab that allow you to set the SCSI ID number from 0 to 7. If you are having trouble getting your PowerLab recognized, try another number and refer to your PowerLab Owner's Guide. This contains a comprehensive section on SCSI and your PowerLab.
When your computer starts up it will look on the SCSI bus to see if there are any SCSI devices connected. This only occurs at start-up, so if your PowerLab is not connected with a unique ID and turned on, then it will not be seen by the computer. If your PowerLab is not recognized, your ADInstruments software will ask you if you want to use Analysis Mode or scan for a PowerLab. Before scanning, you need to ensure you have a unique SCSI ID and that your PowerLab is turned on.
In Windows, if you do connect your PowerLab after you have booted your computer, then you can force Windows 95, 98, ME, 2000 and XP to search for SCSI devices by using the device manager. If a rescan does not work, then try rebooting your computer, again with the PowerLab turned on and with a unique SCSI ID.
You can use Analysis Mode any time as it does not require any interaction with the PowerLab.
SCSI devices, including PowerLabs, also require SCSI drivers to be installed on the computer before the device is recognized. ADInstruments applications (LabChart, Scope) install the appropriate drivers for PowerLab. Therefore, you need to install your ADInstruments application before connecting your PowerLab, otherwise it may not be recognized when you boot your machine.
SCSI Termination
SCSI devices must be terminated before they will work reliably.
This is because the high-speed signals used by SCSI will
reflect back from an unterminated connector and cause data
corruption. Termination problems can result in strange
behaviour and unexplained crashes.
Terminating PowerLabs
There are two types of PowerLab SCSI interfaces. One has
two SCSI connectors (50 pin), and the other has a single
SCSI connector (25 pin).
- Two SCSI Connectors - these PowerLabs do not have a termination
switch and must be terminated in one of two ways. You can
either connect a 25 pin terminator (as supplied with your
PowerLab), to the second connector, or you can connect
another SCSI device (such as another PowerLab), to the
second SCSI connector.
Note: the final device in any daisy chain must be terminated.
- Single SCSI Connector and Termination Switch - to terminate
these PowerLabs, simply ensure that the termination switch
is on (down). These PowerLabs are usually the last device
in any daisy chain or the only SCSI device connected to
your computer. If required, single SCSI PowerLabs can be
daisy chained using a T-cable adapter.
SCSI Cards (Adapters) and Drivers
If you do not have SCSI built in to your computer and you
want to use a SCSI PowerLab, then you will need to use
a SCSI card (also known as a SCSI adapter). If you are
using a SCSI card then you may need to install a SCSI driver
for that card. If appropriate SCSI card drivers are not
installed, then your SCSI card will not be recognised by
your computer and your PowerLab will not be recognised
either. The appropriate SCSI card for PowerLabs is available
from your nearest ADInstruments
representative.
Windows
If you are using Windows 95, 98, ME, 2000 or XP the driver
may already be available as part of your operating system.
If not, you may be able to download the driver from the
card manufacturer's web site.
As well as the appropriate drivers, Windows computers also
require ASPI to allow applications to talk to SCSI devices.
Windows 98 and 95 install ASPI files as part of the operating
system. Windows NT4, 2000 and XP do not. ASPI files may already
be installed on these computers, however, for another reason.
ASPI is also shipped on the ADInstruments software installer
CD along with a read me file outlining how to install ASPI.
ADInstruments supply Adaptec 2906 SCSI cards for SCSI PowerLabs that are to be used with Windows.
Macintosh
ADInstruments supply the Adaptec 2906 SCSI adapter with SCSI
PowerLabs that are to be used with a Macintosh. The latest
Adaptec SCSI card drivers can be downloaded from the Products
section of the Adaptec web site: www.adaptec.com.
Make sure that you download and use the appropriate drivers
for your SCSI card and system. For more information on SCSI
cards compatible with PowerLabs, contact your local ADInstruments
representative.
SCSI Cables
The quality of your SCSI cable is important for reliable
data transfer. To maximise the reliability of your PowerLab
system, always use an approved, high-quality SCSI cable.
Using a non-standard, poor-quality cable will only result
in unreliability and frustration. To improve reliability,
minimise the number of SCSI devices and connectors used,
avoid joining cables together, and minimise cable length.
SCSI Do's and Don'ts
- Never connect or disconnect your PowerLab to or from
your computer while the PowerLab is turned on. You should
always turn your computer off before connecting or disconnecting
your SCSI cable to or from your computer.
- Always use a good quality, standard SCSI cable.
- Always obey termination and SCSI ID rules for your SCSI
devices.
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