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GPIO HWIP Technical Specification

gpio:

Overview

This document specifies GPIO hardware IP functionality. This module conforms to the Comportable guideline for peripheral device functionality See that document for integration overview within the broader top level system.

Features

  • 32 GPIO ports
  • Configurable interrupt per GPIO for detecting rising edge, falling edge, or active low/high input
  • Two ways to update GPIO output: direct-write and masked (thread-safe) update

Description

The GPIO block allows software to communicate through general purpose I/O pins in a flexible manner. Each of 32 independent bits can be written as peripheral outputs in two modes. Each of the 32 bits can be read by software as peripheral inputs. How these peripheral inputs and outputs are connected to the chip IO is not within the scope of this document. See the Comportability Specification for peripheral IO options at the top chip level.

In the output direction, this module provides direct 32b access to each GPIO value using direct write. This mode allows software to control all GPIO bits simultaneously. Alternately, this module provides masked writes to half of the bits at a time, allowing software to affect the output value of a subset of the bits without requiring a read-modify-write. In this mode the user provides a mask of which of the 16 bits are to be modified, along with their new value. The details of this mode are given in the Programmers Guide below.

In the input direction, software can read the contents of any of the GPIO peripheral inputs. In addition, software can request the detection of an interrupt event for any of the 32 bits in a configurable manner. The choices are positive edge, negative edge or level detection events. A noise filter is available through configuration for any of the 32 GPIO inputs. This requires the input to be stable for 16 cycles of the module clock before the input register reflects the change and interrupt generation is evaluated. Note that if the filter is enabled and the pin is set to output then there will be a corresponding delay in a change in output value being reflected in the input register.

See the Design Details section for more details on output, input, and interrupt control.