IDT 89HPES16NT2, User Manual

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Notes
PES16NT2 User Manual 8 - 1 April 15, 2008
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Chapter 8
General Purpose I/O
Introduction
The PES16NT2 has eight General Purpose I/O (GPIO) pins that may be individually configured as:
general purpose inputs, general purpose outputs, or alternate functions. GPIO pins are controlled by the
General Purpose I/O Control and Status (GPIOCS) register located in upstream port A’s PCI configuration
space (see Table 8.1).
GPIO Registers
As shown in Table 8.2, GPIO pins [1,2,4,5] are shared with other on-chip functions. The GPIO Function
(GPIOFUNC) field in the GPIOCS register controls whether a GPIO bit operates as a general purpose I/O
or as the specified alternate function.
Bit
Field
Field
Name
Type
Default
Value
Description
7:0 GPIOFUNC RW 0x0 GPIO Function. Each bit in this field controls the corre-
sponding GPIO pin. When set to a one, the corresponding
GPIO pin operates as the alternate function as defined in
Table 8.2. When a bit is cleared to a zero, the correspond-
ing GPIO pin operates as a general purpose I/O pin.
15:8 GPIOCFG RW 0x0 GPIO Configuration. Each bit in this field controls the cor-
responding GPIO pin. When a bit is configured as a gen-
eral purpose I/O pin and the corresponding bit in this field
is set, the pin is configured as a GPIO output. When a bit
is configured as a general purpose I/O pin and the corre-
sponding bit in this field is zero, the pin is configured as an
input. When the pin is configured as an alternate function,
the behavior of the pin is defined by the alternate function.
23:16 GPIOD RW HWINIT GPIO Data. Each bit in this field controls the correspond-
ing GPIO pin. Reading this field returns the current value
of each GPIO pin regardless of GPIO pin mode (i.e., alter-
nate function or GPIO pin). Writing a value to this field
causes the corresponding pins which are configured as
GPIO outputs to change state to the value written.
31:24 Reserved RO 0x0 Reserved field.
Table 8.1 General Purpose IO Registers