Siemens SIMATIC Rack PC 840 Manual page 152

Controller
Initiate Wide Negotiation
When Initiate Wide Negotiation is set, the SCSI controller uses fast 6-bit data
transfer (wide SCSI) instead of the slower 8-bit data transfer.
Disable Initiate Wide Negotiation only if you are not using wide SCSI devices or if
there are operating problems with 8-bit SCSI devices. You may have to change
some settings on your SCSI devices (read your SCSI device documentation).
Fast SCSI devices, including the SCSI controller, can cope with data transmission
rates to and from the SCSI bus of up to 40 Mbytes/s.
Yes
No
Maximum Sync Transfer Rate
Fast SCSI devices (Ultra Wide) including the SCSI controller, support a data
transfer rate on the SCSI bus of up to 40 Mbytes/s with synchronous data transfer.
If you select Enabled in the Support for Ultra SCSI Speed menu option, a transfer
rate of 40 Mbytes/s is set automatically.
Enable Disconnection
This function allows SCSI devices to release the SCSI bus while a command is
being carried out. A typical example for use of this function is a tape drive that
does not need to access the SCSI bus while being rewound and can be
disconnected from the SCSI bus during this process.
You can disable the function if you have only one SCSI device connected. In this
case, disabling will improve performance.
Yes
No
Send Start Unit Command
If this function is enabled, SCSI devices supporting this function will not be started
until you receive the Start Unit Command from the SCSI BIOS. In this way the
SCSI devices can be switched on one after the other. This function is used if the
power supply to your system is not sufficient to start a number of drives at the
same time or in order to avoid peak turn-on currents.
You may have to change the settings on your SCSI devices so that this function is
supported (read your SCSI device documentation).
Yes
No
8-8
The function is enabled (default setting).
The function is disabled.
The function is enabled (default setting).
The function is disabled.
The function is enabled.
The function is disabled.
SIMATIC Rack PC 840 Manual
A5E00104826-03