Intel cPCI-7200 - Manual (Page 28)

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• Installation
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.
2.9 Onboard 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.
Figure 2.8 Digital input pull-up resistor and termination circuit diagram
.
GND
Digital input
D-type
Flip-Flop
D Q
VCC