The COM Express form factor module are specified by PCI Industrial Computer Manufacturer Group ([http://www.picmg.org PICMG]).

Overview

* Basic Module size of 95x125mm. * Supports: PCI Express (PCIe), SATA, USB 2.0, Gigabit Ethernet, Express Card * There are five different pinout types. Type 2 pinout is the preferred choice. * Connector: two 8mm stack height 440 pin (bridged 220 pin pair): Tyco 3-5353652-6 or Tyco 8-1318491-6

Kontron's ETXexpress provide (Congatec is in parentheses if different): * 5 PCIe lanes (Congatec: 6 PCIe) * 2 SATA ports (Congatec: 4 SATA) * 2 ExpressCard Control * 8 USB 2.0 ports * AC'97 Digital Audio * Low Pin Count (LPC) control * Graphics: LVDS, VGA, TV-Out (Composite, Component, S-Video) * PCI Express Graphics (PEG)

We will use the Kontron Module from here on out.

Signal Overview

PCI Express (PCIe)

COM Express specifies a minimum of 2 (port 0, 1) and a maximum of 6 (port 2 - 5 in order). Each single lane has data transfer rate of 2.5Gbps @ 1.25GHz

Universal Serial Bus (USB)

COM Express specifies a minimum of 4 (port 0 - 3) and a maximum of 8 (port 4 - 7 in order).

There are four USB over-current lines defined in the COM Express™ Specification. The overcurrent lines are shared by ports 0 and 1; by ports 2 and 3; by ports 4 and 5 and by ports 6 and 7.

Route USB signals as differential pairs, with a 90-ohm differential impedance and a 45-ohm, single-ended impedance.

ExpressCard

Requires A PCIe lane and a USB 2.0 port. It also needs a reset and a card request line. COM Express has 2 of these pairs. beobot


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