Slot Selection Switches, PCI Bus Signaling Levels

•PCI bus expansion card power

•PCI bus signaling levels

Slot Selection Switches

Unlike PC/104 cards, PC/104-Plusand 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.

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.

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 factory default configuration is to connect the +3.3 V pins on the PCI bus to the auxiliary power connector (CN3) by soldering pins 1–2 on solder blob, B3 (see Table 58 on page 82 for solder blob settings). This is to ensure that the cpuModule’s onboard +3.3V supply will not supply power to the PC/104-Plusconnector while a PC/104-Plusor PCI-104 power supply is already powering the +3.3V pins.

To supply +3.3V to PC/104-Plusor PCI-104 expansion boards with the onboard +3.3 V power supply, change B3 from pins 1–2 to pins 2–3. In this configuration, the current limit of the +3.3V connection to the PCI +3.3V via B3 should not be exceeded (see Table 58 on page 82 for current limitation).

PCI Bus Signaling Levels

The PCI bus can operate at +3.3 V or +5 V signaling levels. The signaling levels for the I/O pins on a PCI bus card are determined by solder blob B1. The default is +3.3 V. Refer to Table 58 on page 82 for solder blob settings.

WARNING You will have to ensure that all your expansion cards can operate together at a single signaling level.

BDM-610000050 Rev A

Chapter 2: Getting Started 19