SMSC LAN9311, LAN9311i manual 194

Two Port 10/100 Managed Ethernet Switch with 16-Bit Non-PCI CPU Interface

Datasheet

BITS			DESCRIPTION		TYPE	DEFAULT
11:0	GPIO Buffer Type 11-0 (GPIOBUF[11:0])				R/W	0h
	This field sets the buffer types of the 12 GPIO pins.
	0: Corresponding GPIO pin configured as an open-drain driver
	1: Corresponding GPIO pin configured as a push/pull driver
	As an open-drain driver, the output pin is driven low when the corresponding
	data register is cleared, and is not driven when the corresponding data
	register is set.
	As an open-drain driver used for 1588 Clock Events, the corresponding
	GPIO_EVENT_POL_8 and GPIO_EVENT_POL_9 bits determine when the
	corresponding pin is driven per the following table:
		GPIOx Clock Event Polarity	1588 Clock Event	Pin State
		0	no	not driven
		0	yes	driven low
		1	no	driven low
		1	yes	not driven

Revision 1.4 (08-19-08)	194	SMSC LAN9311/LAN9311i
	DATASHEET