Kontron COMe Starterkit Eval T2 - Manual (Page 44)

COM Express Interfaces
Figure 14: PCIe Mini Card Reference Circuitry
A PCI Express Mini Card schematic example is shown in Figure 14 above. The reference clock
pair is sourced from the zero delay clock buffer shown earlier in Figure 6 'PCIe Reference Clock
Buffer' on page 35 above. The clock pair is enabled when the PCI Express Mini-Card pulls its
CLKREQ# pin low.
The example shows COM Express PCIe lane 1 and USB port 0 used, but other assignments
may be made depending on Module capabilities and the system configuration.
If Suspend mode operation is not required, then the 3.3VAUX pin may be tied to VCC_3V3. The
WAKE# pin should be left open in this case.
2.3.5.8. ExpressCard
ExpressCards are small form factor hot-swappable peripheral cards designed primarily for
mobile computing. The card’s electrical interface is through either a x1 PCIe link or a USB 2.0
link. Per the ExpressCard source specification, the host interface should support both the PCIe
and USB links. The ExpressCard device may utilize one or the other or both interfaces.
There are several form factors defined, including: 34mm x 75mm; 54mm x 75mm; 34mm x
100mm, and 54mm x 100mm. All of the form factors use the same electrical and physical socket
interface.
ExpressCards are the successor to Card Bus Cards (which are PCI-based). Card Bus cards, in
turn, are the successors to PCMCIA cards. All three formats are defined by the PCMCIA
Consortium.
The source specification document for ExpressCards is the ExpressCard Standard.
COM Express includes four signals that are designated for the support of two ExpressCard slots:
PICMG ® COM Express ® Carrier Board Design Guide Rev. 2.0 / December 6, 2013
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VCC_3V3_SBY
VCC_1V5
PCIE_CLK_REQ0#
CEX
PCIE_TX1+ CEX
PCIE_TX1-
SMB_CK_S0
SMB_DAT_S0
CEX
USB0+ CEX
USB0-
CEX
PCIE_RX1+ CEX
PCIE_RX1-
CEX
WAKE0# CEX
PCIE_RESET1#
PCIE_CLK_REF0+
PCIE_CLK_REF0-
C9
4.7uF
C8
100n
C11
4.7uF C10
100n
PCIe Mini-Card Connector
J3
PCIe Mini-Card Connector
W_DISABLE2# 51
RSVD2 49 RSVD3 47 RSVD4 45
GND
43
41
39
37
GND
35
PET0+ 33
PET0- 31
GND
29
GND
27
PER0+ 25
PER0- 23
GND
21
UIM_IC_DP 19
UIM_IC_DM 17
GND
15
REFCLK+
13
REFCLK-
11
GND
9
CLKREQ# 7
COEX2 5 COEX1 3
WAKE# 1
52
GND
50
1.5V
48
LED_WPAN# 46
LED_WLAN# 44
LED_WWAN# 42
GND
40
GND
34
SMB_DATA
32
SMB_CLK 30
1.5V
28
GND 26
3.3VAUX 24
PERST# 22
W_DISABLE1# 20
GND
18
UIM_SPU 16
UIM_RESET 14
UIM_CLK 12
UIM_DATA 10
UIM_PWR 8
1.5V
6
GND
4
2
USB_D+ 38
USB_D- 36
SH1 S1
SH2 S2
SH3 S3
SH4 S4
SH5 S5
SH6 S6
3.3VAUX
3.3VAUX
3.3VAUX
3.3VAUX
GND