Intel 815 manual Gpio Registers, GPIOAGeneral Purpose I/O Control Register a

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

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19.2.GPIO Registers

19.2.1.GPIOAGeneral Purpose I/O Control Register A

Address offset :	05010h
Default value :	00h, 00h, 000U0000b, 000U0000b
Access :	Read / write
Size :	32 bit

This register controls the general purpose I/O pins DDCK and DDDA, which are used to create a Display Data Channel (DDC) serial bus for communication with an external analog display monitor.

31						16
		Reserved
15	13	12	11	10	9	8
	Reserved	DDDA	DDDA	DDDA	DDDA	DDDA
		Data In	Data value	Data Mask	Direction	Direction
					value	Mask
7	5	4	3	2	1	0
	Reserved	DDCK	DDCK	DDCK	DDCK	DDCK
		Data In	Data value	Data Mask	Direction	Direction
					value	Mask
Bit			Description
31:16	Reserved.
15:13	Reserved.
12	DDDA Data In—RO:This is the value that is sampled on the DDDA pin as an input.
	The Data In bits [12], [4] of the GPIOA (GPIOB) register are read only, however, data is only latched
	into these bits when a write is done to the respective bytes of the GPIOA (GPIOB) register. Thus a
	read of the Data In bits must be preceded with a dummy write.
11	DDDA Data Value—R/W:This is the value that should be place on the DDDA pin as an output. This
	value is only written into the register if DDDA DATA MASK is also asserted. The value will appear on
	the pin if this data value is actually written to this register and the DDDA DIRECTION VALUE contains
	a value that will configure the pin as an output.
10	DDDA Data Mask—R/W:This is a mask bit to determine whether the DDDA DATA VALUE bit should
	be written into the register.
	0 = Do NOT write DDDA Data Value bit (default).
	1 = Write DDDA Data Value bit.
9	DDDA Direction Value—R/W:This is the value that should be used to define the ouput enable of the
	DDDA pin. This value is only written into the register if DDDA DIRECTION MASK is also asserted. The
	value that will appear on the pin is defined by what is in the register for the DDDA DATA VALUE.bit.
	0 = Pin is configured as an input (default)
	1 = Pin is configured as an output.

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