Siemens SIMATIC Rack PC 840 V2 Operating Instructions Manual page 133

"PCI Devices" field
If the PCI devices field is selected, the following submenu appears:
Figure 16-15 PCI Devices submenu, slot #1
ROM scan option:
Enable Master
Latency Timer
SIMATIC Rack PC 840 V2
Operating Instructions, Edition 05/2006, A5E00248055-04
[Enabled]
[Disabled]
[Enabled]
[Disabled]
[Default]
[0020H to 00E0H]
You should only use a value different from the default if the module or its
application requires it.
The Option ROM of the PCI module (if present) is
enabled
The ROM option of a PCI module is disabled.
This slot can be assigned master functions
This slot can only operate as a PCI slave.
The number of active PCI clock cycles of the
master modules is determined by this module
With these settings, you set the maximum number
of active PCI clock cycles to the selected value.
Detailed descriptions
16.5 BIOS Setup
16-35