Siemens SIMATIC Rack PC 840 Manual page 147

Caution
Only SCSI devices with a single ended interface may be connected to the SCSI
controller. Most SCSI devices meet this requirement. Contact your supplier or our
customer service staff if in doubt.
Connectors and Cables
The integrated SCSI controller has the following connectors.
• Internal 16-bit 68-pin connector socket (UW SCSI bus)
• Internal 8-bit 50-pin connector plug (U SCSI bus)
• 4-pin LED connection plug
• External 16-bit 68-pin connector socket (UW SCSI bus)
Only two of the controller's SCSI connections may be assigned at the one time.
The integrated hard disk is connected at the internal 16-bit connector.
Read "Connecting Other SCSI Devices" for more information on expanding the
system.
internal 16-bit
68-pin connector
external 16-bit
68-pin connector
8-bit SCSI devices have a 50-pin connector, and 16-bit SCSI devices have a
68-pin connector.
You need an adapter (68-pin to 50-pin) if you want to connect 8-bit SCSI devices to
the SCSI controller.
If you are operating an 8-bit SCSI device as the final device on the SCSI cable you
need an adapter (68-pin to 50-pin) with high-byte termination.
Notice
Use top-quality SCSI cables only as otherwise you may have problems
transferring data.
SIMATIC Rack PC 840 Manual
A5E00104826-03
4-pin LED
connector
internal 8-bit
50-pin connector
Controller
8-3