C2K User’s Guide
5-16
Resources
5.2.3 GPIO Registers
The C2K includes 16 General-Purpose Input/Output ports. The FPGA provides the GPIO inter-
rupt masking, data, and control registers for configuring, masking interrupts, and sending/receiv-
ing data on the GPIO lines connected to the backplane. The FPGA also includes an optional
de-bounce circuit that can be applied to each port designated as an input for use with external
switches, contacts, or relays. The GPIO registers set the following configuration parameters:
• Direction (input or output)
• Output drive type (TTL or open-drain)
• Input polarity (inverted or non-inverted)
• Interrupt type (edge or level-sensitive)
• Debounce filter on input
When the GPIO lines are configured as outputs, they can be driven as either standard TTL or
open-drain (drive-low only). When configured as inputs, the GPIO lines can be treated as positive
or negative logic and can be enabled as either edge or level-type interrupt sources for generating
the MPC7448 processor’s interrupt input (the FPGA interrupt output passes through the
MV64460 interrupt logic). The selected logic polarity for GPIO inputs affects the value read in
the GPIO Data Register and affects which logic level will cause an interrupt assertion. The regis-
ters’ default bit values occur after a power-up reset.
Table 5-9 lists the GPIO registers.
Table 5-9
GPIO registers
Offset
Register
Description
0x30
GPIO Direction
Enables a direction for each GPIO line.
0x32
GPIO Polarity
Enables polarity for each GPIO line.
0x34
GPIO Output Type
Enables output type for each GPIO line.
0x36
GPIO Interrupt Type
Configures each interrupt for type (edge, level)
0x38
GPIO De-Bounce Enable Enables a de-bounce circuit for each GPIO line.
0x40
GPIO Input Data Read
Enables input data read for each GPIO line.
0x42
GPIO IO Data
Enable input IO data state for each GPIO line.
0x44
GPIO Interrupt Status
Provides the interrupt status for each GPIO line.
0x46
GPIO Interrupt Mask
Enables interrupt masking for each GPIO line.
0x4C
GPIO Clear
Clears the GPIO bit for each GPIO line.
0x4E
GPIO Set
Sets the GPIO bit for each GPIO line.
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
