Intel manual LPCI-7200S PCI Bus Signaling, Onboard Pull-ups and Terminations in digital input

2.8 LPCI-7200S PCI Bus Signaling

Low-Profile PCI is a new PCI card standard for space-constrained system designs. The new form factor maintain the same electrical protocols, PCI signals, and software drivers as standard PCI v2.2 expansion cards. However, Low-Profile PCI bus interface only supports 3.3V signaling. To support both 5V and 3.3V signaling, LPCI-7200S implements 5V I/O tolerant bus switches to achieve the I/O voltage transition. This allows LPCI-7200S to be used in both 5V and 3.3V systems.

2.9Onboard Pull-ups and Terminations in digital input

The PCI-7200, cPCI-7200 and LPCI-7200S have 32 digital input channels. On-board pull-ups and terminations for digital input circuits may be needed for some applications. The pull-ups guarantee a fixed input state when external connections are floating. Schottky terminations can minimize undershoot/overshoot disturbances caused by reflection noise on high-speed bus lines. Table 2.1 lists the pull-ups and termination status of PCI-7200, cPCI-7200 and LPCI-7200S. Figure 2.8 is the illustration of the pull-up resistor and terminations on-board.

	Pull-up resistor	Terminations
PCI-7200	None	None
cPCI-7200	None	Schottky diode clamped
		to ground & power
LPCI-7200S	10kΩ	Schottky diode clamped
		to ground & power

Table 2.1 pull-ups and termination of PCI/cPCI-7200 and LPCI-7200S.

VCC

Digital input

D-type

Flip-Flop

D Q

GND

Figure 2.8 Digital input pull-up resistor and termination circuit diagram.

20 • Installation