3.0 Electrical Interfaces
Fusion 878A
3.3 General Purpose I/O Port
PCI Video Decoder
3-10
Conexant
100600B
3.3 General Purpose I/O Port
3.3.1 GPIO Pin Architecture
Each GPIO pin is set up as a basic input/output buffer, with each bit of the GPOE
register used to enable an individual pin’s output driver (refer to
).
3.3.2 GPIO Modes in Fusion 878A
The GPIO port operates in five designated modes:
•
Normal mode
•
Synchronous Pixel Interface (SPI) Input mode
•
SPI Output mode
•
Digital Video Input mode
•
Asynchronous Data Parallel mode
The GPIOMODE bits determine the port’s mode of operation. Each GPIO pin
can be individually configured, but GPIOMODE affects the entire port.
3.3.3 GPIO Normal Mode
The Normal mode of the GPIO port can be used to input or output general
board-level signals to or from the PCI interface in the Fusion 878A. The
GPIOMODE bits are in the default state of 00 during Normal mode. The GPIO
port in Normal mode was not designed to support a high-speed interface for video
data or other types of data. The functionality of the GPIO in Normal mode is
illustrated in
Figure 3-6. GPIO Pin Architecture
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GPDATA Input/
Read Buffer/Register
GPDATA Output/
Write Holding Register
GPOE[N]
Three-State
Buffer
Pin N
879A_057