Kontron COMe Starterkit Eval T2 - Manual (Page 50)

COM Express Interfaces
2.4.2.1. Using PEG Pins for an External Graphics Card
To use the COM Express PEG lanes for an external graphics device or card, the Type 2 Module's
PEG_ENABLE# line (pin D97 on the Module C-D connector) must be pulled low. Pulling this pin
low disables the Module's internal graphics controller and makes the PEG x16 interface available
to an external controller.
The usual effect of pulling PEG_ENABLE# low is to disable the on-Module graphics engine. For
some Modules, it is possible to configure the Module such that the internal graphics engine
remains active, even when the external PEG interface is being used for a Carrier Board graphics
device. This is Module dependent. Check with your vendor.
If the external graphics controller is “down” on the Carrier Board, then the PEG_ENABLE# line
should be pulled to GND on the Carrier Board.
There are four copies of PRSNT2# defined for slot cards, to allow detection of x1, x4, x8 and x16
cards. For PEG slot use, the PRSNT2# signals for the x1 and x4 links are used for SDVO
detection per the following chart.
To enable carrier flexibility in slot configuration and to support x1, x4, x8 and x16 PCI Express
cards as well as ADD2/MEC cards and MEC cards that utilize both SDVO and x1 PCI Express, a
jumper is recommended on the carrier to configure the PEG_ENABLE# signal. For carrier
implementations only requiring support of x8 and x16 PCI Express graphics cards and SDVO
ADD2 cards, the PRSNT2# signals on slot pins B48 and B81 may be tied to COM Express
Module PEG_ENABLE# pin D97 to automatically configure the Module based on the card
inserted.
Table 10: PEG Configuration Pins
Slot
Signal Slot
Pin Carrier Board Connection COM Ex
Pin Comment
PRSNT1# A1 Tie to GND through low value
resistor Pins A1, B48 and B81 are tied together on a
PEG slot card. Not tied together on ADD2.
PRSNT2# B17 To COM Ex SDVO_I2C_CLK line D73 SDVO use – pulled to 2.5V on ADD2
PRSNT2# B31 To COM Ex SDVO_I2C_DAT line C73 SDVO use – pulled to 2.5V on ADD2
PRSNT2# B48 Not connected
PRSNT2# B81 To COM Ex PEG_ENABLE#
2.4.2.2. Using PEG Pins for SDVO (Type 2 Modules only)
The COM Express Module graphics controller configures the PEG lines for SDVO operation if it
detects that COM Express signals SDVO_I2C_CLK and SDVO_I2C_DATA are pulled high to
2.5V, and if the PEG_ENABLE# line is left floating. This combination leaves the Module's
internal graphics engine enabled but converts the output format to SDVO. The SDVO_I2C_CLK
and SDVO_I2C_DATA lines are pulled to 2.5V on an ADD2 card.
For a device “down” SDVO converter, the SDVO_I2C_CLK and SDVO_I2C_DATA lines have to
be pulled up to 2.5V on the Carrier Board.
2.4.2.3. Using PEG Pins for General Purpose PCIe Lanes
The COM Express PEG lanes may be used for general-purpose use if the PEG port is not being
used as an interface to an external graphics device. The characteristics of this usage are Module
and chip-set dependent.
PICMG ® COM Express ® Carrier Board Design Guide Rev. 2.0 / December 6, 2013
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