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BDM-610000049 Rev G Chapter 2: Getting Started 21
• PCI bus expansion card power
• PCI bus signaling levels
Slot Selection Switches
Unlike PC/104 cards, PC/104-Plus and PCI-104 expansion cards have a “slot” selection switch or jumpers. In total,
there are 4 PCI cards that can be stacked onto the cpuModule with switch positions 0 through 3. The distance
from the CPU determines these switch settings. The card closest to the CPU is said to be in slot 0, the next closest
slot 1 and so on to the final card as slot 3.
The “slot” setting method may vary from manufacturer to manufacturer, but the concept is the same. The CPU
is designed to provide the correct delay to the clock signals to compensate for the bus length. The correct switch
setting ensures the proper clock delay setting, interrupt assignment, and bus grant/request channel assignment.
Refer to the expansion board’s manual for the proper settings. Each expansion card must be in a different slot.
PCI Bus Expansion Card Power
+5 Volt DC
The +5 V power pins on the PC/104-Plus (PCI) bus are connected directly to the +5 V pins on the auxiliary power
connector, CN3 (pins 2 and 8).
+3.3 Volt DC
The +3.3V pins on the PCI bus can be configured to be supplied from the power connector (CN3) or the onboard
+3.3V power supply. The factory default configuration connects the +3.3 V pins on the PCI bus to the auxiliary
power connector (CN3). This is to ensure that the cpuModule’s onboard +3.3V supply will not supply power to
the PC/104-Plus connector while a PC/104-Plus or PCI-104 power supply is already powering the +3.3V pins.
For more information on configuring the +3.3V pins on the PCI bus, contact RTD Technical Support.
PCI Bus Signaling Levels
The PCI bus can operate at +3.3 V or +5 V signaling levels. The default PCI bus signaling level is +3.3 V. For more
information, contact RTD Technical Support.
Note This requirement means that all PC/104-Plus and PCI-104 cards must be stacked either on the top
or the bottom of the CPU, not on both sides.
WARNING You will have to ensure that all your expansion cards can operate together at a single
signaling level.