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==== General Purpose Input and Output Port (GPIO)

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| Hardware source file(s): | neorv32_gpio.vhd |

| Software driver file(s): | neorv32_gpio.c |

|                          | neorv32_gpio.h |

| Top entity port:         | `gpio_o` | 64-bit parallel output port

|                          | `gpio_i` | 64-bit parallel input port

| Configuration generics:  | _IO_GPIO_EN_ | implement GPIO port when _true_

| CPU interrupts:          | none |

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**Theory of Operation**

The general purpose parallel IO port unit provides a simple 64-bit parallel input port and a 64-bit parallel

output port. These ports can be used chip-externally (for example to drive status LEDs, connect buttons, etc.)

or system-internally to provide control signals for other IP modules. The component is disabled for

implementation when the _IO_GPIO_EN_ generic is set _false_. In this case GPIO output port is tied to all-zero.

.Access atomicity

[NOTE]

The GPIO modules uses two memory-mapped registers (each 32-bit) each for accessing the input and

output signals. Since the CPU can only process 32-bit "at once" updating the entire output cannot

be performed within a single clock cycle.

.GPIO unit register map (`struct NEORV32_GPIO`)

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| Address      | Name [C]         | Bit(s) | R/W | Function

| `0xffffffc0` | `NEORV32_GPIO.INPUT_LO`  | 31:0   | r/- | parallel input port pins 31:0 (write accesses are ignored)

| `0xffffffc4` | `NEORV32_GPIO.INPUT_HI`  | 31:0   | r/- | parallel input port pins 63:32 (write accesses are ignored)

| `0xffffffc8` | `NEORV32_GPIO.OUTPUT_LO` | 31:0   | r/w | parallel output port pins 31:0

| `0xffffffcc` | `NEORV32_GPIO.OUTPUT_HI` | 31:0   | r/w | parallel output port pins 63:32

|=======================