Artesyn COMX-P40x0 ENP2, Manual

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Functional Description
COMX-P40x0 ENP2 Installation and Use (6806800R95B )
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An optional fifth USB port can be provided from the CPU through a ULPI USB PHY (USB3315)
to the COM Express connector. This is the default option for modules not providing the 1GE
port since the two functions are multiplexed on the same CPU pins. An active-low overcurrent
signal USB_OC_4_5_N is provided from the COM Express connector to indicate a power fault
on the fifth USB port. It is routed as an interrupt to the CPU.
4.18 I2C Interface
The P40x0 CPU has four I2C buses. Among four I2C buses, the I2C3 bus is multiplexed with
SDHC bus and remaining I2C buses are routed to the COM Express connectors.
There is only one device attached to the second I2C bus I2C2, and there are 6 devices attached
to the first I2C bus I2C1.